Possible Planet of Gliese 436 May Be Melting...

The above image is an artist's concept of exoplanet candidate UCF-1.01 orbiting the red dwarf star Gliese 436 (GJ 436). The surface of UCF-1.01 is depicted with flowing magma. Image Credit: NASA

Astronomers using NASA's Spitzer Space Telescope have detected what they believe to be a planet that is just two-thirds the size of Earth — one of the smallest on record. The exoplanet candidate, known as UCF-1.01, orbits a red dwarf (spectral type M2.5 V) star called Gliese 436 (GJ 436), which is located just 33.1 light-years away. UCF-1.01 might be the nearest world to our solar system that is smaller than our home planet.

Exoplanets (extra-solar planets) orbit other stars. So far, only a handful have been found that are smaller than Earth. Spitzer has performed transit studies on known exoplanets, but UCF-1.01 is the first ever identified using the space telescope, suggesting a possible role for Spitzer in helping discover potentially habitable, terrestrial-sized worlds.


The potential planet is very small, very hot and very near to its parent star. A paper on the discovery has been accepted for publication in The Astrophysical Journal. The lead author of the paper is Kevin Stevenson from the Unversity of Central Florida in Orlando. His co-author is Joseph Harrington, also of the University of Central Florida, who is also the principal investigator of the research. The Astrophysical Journal may be visited online by CLICKING HERE.

The exoplanet candidate was found unexpectedly in Spitzer observations and may become the second known planet in the GJ 436 system. Stevenson and his colleagues were studying the Neptune-sized exoplanet GJ 436b, already known to orbit GJ 436. In the Spitzer data, the astronomers noticed slight dips in the amount of infrared light streaming from the star, separate from the dips caused by GJ 436b. A review of Spitzer archival data showed the dips were periodic, suggesting a second planet might be orbiting the star and blocking out a small fraction of the star's light.


This technique of tracking dips in starlight, used by a number of observatories including NASA's Kepler space telescope. It relies on transits to detect exoplanets. The duration of a transit and the amount of the decrease in light reveals basic properties of an exoplanet, such as its size and distance from its star. In UCF-1.01's case, its diameter would be approximately 5,200 miles (8,400 kilometers). That would make the planet size about two-thirds that of Earth, or roughly half-way between Mars and Venus. UCF-1.01 would revolve quite tightly around GJ 436, at about seven times the distance of Earth from the moon, with its "year" lasting only 1.4 Earth days. Given this proximity to its star, far closer than the planet Mercury is to our sun, the exoplanet's surface temperature would be more than 1,000 degrees Fahrenheit (almost 600 degrees Celsius).

If UCF-1.01 ever had an atmosphere, it almost surely has evaporated. Some suggest its appearance might resemble a cratered, mostly geologically dead world like Mercury. But the researchers suggest that the extreme heat of orbiting so close to GJ 436 has melted the exoplanet's surface, and the planet might even be covered in magma.

In addition to UCF-1.01, the research team noticed hints of a third planet, dubbed UCF-1.02, orbiting GJ 436. Spitzer has observed evidence of the two new planets several times each. However, even the most sensitive instruments are unable to measure exoplanet masses as small as UCF-1.01 and UCF-1.02, which are perhaps only one-third the mass of Earth. Knowing the mass is required for confirming a discovery, so the researchers are cautiously calling both bodies exoplanet candidates for now.

Of the approximately 1,800 stars identified by NASA's Kepler space telescope as candidates for having planetary systems, just three are verified to contain sub-Earth-sized exoplanets. Of these, only one exoplanet is thought to be smaller than the Spitzer candidates, with a radius similar to Mars, or 57 percent that of Earth. The researchers hope that future missions which are better designed for the task, will confirm their results. That being said, scientists are singing the praises of the nine-year-old Spitzer mission, which may be able to discover exoplanets as small as Mars.

And now, the mission particulars...

NASA's Jet Propulsion Laboratory (JPL), Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. To learn more about Spitzer, visit http://www.spitzer.caltech.edu/ and www.nasa.gov/spitzer .

More information about exoplanets and NASA's planet-finding program is at planetquest.jpl.nasa.gov .

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NuSTAR: Science Overview

The above image is a promotional sticker for NASA's NuSTAR mission. Organization affiliations are displayed around the border of the sticker. Image Credit: NASA/JPL-Caltech

We now continue our review of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, which launched June 13th. In this outing, we get an overview of the NuSTAR mission science...

Science Overview

NuSTAR will dramatically change the way astronomers view the high-energy X-ray sky. The mission’s main objective is to obtain detailed images of regions of the sky at these energies. Despite NuSTAR’s small size and low cost, it will have more than 10 times better resolution and more than 100 times better sensitivity than any previous mission working in this high-energy regime.

The five primary science goals for its two-year baseline mission are:

• to locate supermassive black holes;
• to locate the remnants of collapsed stars;
• to map historic supernova remnants;
• to observe high-energy gamma-ray sources; and
• to quickly observe supernovae in the local universe right after they happen, should they occur during the mission’s lifetime.

Black Holes

When enough matter is packed into a small region, it inevitably collapses to form a black hole — a tear in the fabric of space-time. The name “black hole” comes from the fact that even light cannot escape the overpowering grasp of the matter’s gravity. Black holes formed in the early universe, and by “swallowing” matter, stars and even other black holes, they grew over the course of cosmic time. Smaller black holes are also being created throughout the cosmos as massive stars end their lives. When a massive star explodes, it hurtles matter into space; if the star is massive enough, then its core will collapse into a black hole.

When a black hole “feeds” from matter falling onto it, the matter forms a swirling disk, heats up to very high temperatures and then disappears from view forever. The hot matter reaches up to hundreds of millions of degrees in temperature and radiates copious amounts of X-rays.

NuSTAR will search for these telltale X-rays streaming from regions close to the invisible black holes. It will observe known black holes, and discover new ones, of many sizes. The smallest the observatory can see are peppered throughout our Milky Way galaxy, and have masses as low as a few times that of our sun. The largest black holes are formed at the centers of galaxies, and can have masses up to millions or billions of times the mass of our sun. NuSTAR will also observe a poorly understood class of objects known as “ultraluminous X-ray sources,” some of which are considered likely intermediate-mass black holes, with masses a few thousand times that of our sun.

In our galaxy, the mission will probe the crowded center, where unseen black holes are lurking. High-energy X-rays can penetrate deeper through gas and dust than lower-energy X-rays, so NuSTAR will find new, hidden stellar relics. Working in coordination with a vast network of other facilities, including NASA’s Chandra X-ray Observatory, NuSTAR will also peer into the “monster in the middle” of our galaxy, a sleeping supermassive black hole about four million times the mass of our sun, and address questions about its mysterious behavior.

In the distant universe, the mission will spend months hunting for hidden black holes buried in the hearts of dusty galaxies. All galaxies are thought to harbor supermassive black holes at their cores. Most of these, like our Milky Way black hole, are dim at all wavelengths of light. They are sometimes thought of as “sleeping” and are undetectable in even nearby galaxies. However, some fraction of black holes, the so-called active ones, swallow dust and gas and shine brightly. Of these active black holes, about two-thirds are thought to have gone undetected due to obscuring layers of dust. NuSTAR will uncover many of these hidden objects, providing a complete census of active black holes.

NuSTAR data will be used together with that from other telescopes studying different wavelengths, such as NASA’s Hubble Space Telescope (visible light); NASA’s Spitzer Space Telescope (infrared), Chandra and XMMNewton (both low-energy X-rays). Some NuSTAR observing programs will simply use existing, archival data from these other observatories, while other programs will require coordinated scheduling. For example, working with XMM-Newton, NuSTAR is planning to spend several weeks doing coordinated observations of powerful, active galaxies with the goal of making precise measurements of the rate with which their central supermassive black holes are spinning. Such measurements are not possible by either telescope individually, but by working together, NuSTAR and XMM-Newton will inform astronomers about the physical conditions near the galaxy’s central engine, as well as probe how supermassive black holes form.

Surveys of well-studied fields in the sky by NuSTAR will also help solve the enigma of how black holes and galaxies grow and evolve together.

Stellar Corpses

Black holes are the end state of the most massive stars in the universe. Other less massive stars leave behind different types of stellar remnants when they die. For example, stars that aren’t quite big enough to produce black holes, but are still massive enough to explode, result in neutron stars. These are incredibly dense objects. If the sun were a neutron star, its matter would be squeezed into something the size of Pasadena. When neutron stars form, collapsing in supernova blasts, their atoms are crushed, forcing the electrons and protons together, and leaving mainly neutrons.

When even less massive stars die, such as our sun, they don’t fully explode. Instead they puff up into red giants, and then shed their outer layers. The cores of these stars also collapse into compact objects, called white dwarfs.

NuSTAR will search for all of these stellar embers, primarily in the center of our galaxy, as well as examine known ones. When these embers are in binary star systems, they can accrete material from their partners. As this material falls onto the dense core, it heats up, radiating high-energy X-rays. The observatory will give astronomers a new tool to study our galaxy’s stellar graveyard, revealing how the remains are distributed.

The mission will look at other types of exotic, dead stars too. One class of neutron star, called magnetars, have the most intense internal magnetic fields known in the universe, quadrillions of times greater than Earth’s. As the magnetic fields decay, powerful bursts are triggered lasting milliseconds to years. NuSTAR will provide new insight into these mysterious, poorly understood objects.

NuSTAR will also probe pulsars, another class of neutron star that send out beams of radiation as they rotate around like a lighthouse beacon. These objects produce powerful winds carrying particles at nearly the speed of light. When the winds hit surrounding material, they heat it up, forming unusual nebulae. NuSTAR will help understand the physics of this dramatic process.

How Do Stars Explode?

Another one of the mission’s goals is to understand how the elements all around us, including the chemicals making up our bodies, were forged inside stars. When the most massive stars explode as supernovae, they synthesize and disseminate a range of elements, including the heaviest ones, such as iron. Without supernovae, there would be no iron circulating around in your blood, nor gold for making jewelry. The heavier elements are also needed to seed new generations of stars.

NuSTAR will offer a new way to examine this cycle of life, death and rebirth in the universe. It will thoroughly study two well-known supernova remnants: Cassiopeia A in our galaxy, and SN 1987A in a small neighboring galaxy. Astronomers using NuSTAR will be able to sift through the remains of these exploded stars by measuring the amount, distribution and speed of radioactive material released by the explosion. In particular, the isotope Titanium 44 (44Ti) is a critical diagnostic of supernova explosions, since it comes from near the “fallback region” of the explosion. Some models predict 44Ti is ejected into the cosmos as part of the colossal explosion. Other models predict that 44Ti fails to reach sufficient speeds to escape, and instead falls back on to the stellar corpse leftover from the blast. NuSTAR observations of historic, nearby supernovae will test these models.

Despite being well studied, exactly how a supernova explosion occurs is still unknown. NuSTAR will help reveal the physics behind the moment when a massive star erupts, lighting up the cosmos like fireworks. Such information is fundamental for understanding how the elements are forged and distributed by these massive explosions.

Energy Extremes

A small fraction of the most exotic supermassive black holes exhibit extreme behavior — spewing out jets of material moving very close to the speed of light. These jets can be so powerful that they choke off the creation of stars, leading to the death of the surrounding galaxy. The processes that create these jets, and which accelerate the high-energy particles within them, are not understood. By teaming up with observatories that see in various bands, from radio to high-energy gamma-rays, NuSTAR will help unravel the exotic physics underlying these extreme black holes.

Witnessing a Star’s Death Throes

Another goal of NuSTAR is to witness a supernova as it unfolds. This would only be possible if such an event occurs during the mission’s lifetime, and at close enough distances for the observatory to see it. A supernova resulting from the death of a massive star is estimated to occur once every 30 years or so in our galaxy. About every five years, a much more luminous type of supernova, believed to result from the violent detonation of a white dwarf star, occurs in the space between our galaxy and the nearest cluster of galaxies, called the Virgo cluster. The 2011 Nobel Prize in Physics was awarded to a team of astronomers who used this second type of explosion to map the expansion history of the universe. Their work provided conclusive evidence that the expansion rate of the universe is increasing, implying the existence of a mysterious force dubbed “dark energy.” NuSTAR observations can shed light on how this detonation happens. Such observations, called targets of opportunity, will be the highest priority for the observatory when they occur.

Other Science

NuSTAR will also observe flaring stars, star-forming galaxies, distant clusters of galaxies and more. Closer to home, it will measure X-rays coming from our sun’s corona — an outer atmosphere consisting of scorching hot gases. The observatory will be much more sensitive to solar X-rays than the previous X-ray mission studying the sun, NASA’s Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and will provide detailed images of flares, loops and other eruptions from the sun’s surface. NuSTAR has the ability to reveal tiny flares on the sun, called “nanoflares,” if they exist, and answer the long-standing mystery of how the solar corona is heated.

As is typical of most NASA Small Explorer missions, during its two-year baseline mission, NuSTAR will not have a Guest Observer program in which members of the larger astronomy community can apply for time on the telescope. However, assuming the continued health of the NuSTAR observatory, the mission team will propose for an extended mission, during which guest investigators can participate in the NuSTAR science.

Key NuSTAR Team Members (Name, Title, Institution):

• Fiona Harrison, Principal Investigator, California Institute of Technology
• Yunjin Kim, Project Manager, Jet Propulsion Laboratory
• Grace Baird, Spacecraft Bus Chief Engineer, Orbital Sciences Corporation
• Manfred Bester, Mission Operations Manager, Space Sciences Laboratory
• Steven Boggs, Co-Investigator, UC Berkeley
• Finn Christensen, Optics Coatings Lead, Danish Technical University
• Whitney Clavin, Media Relations, Jet Propulsion Laboratory
• William Craig, Instrument Manager, Livermore National Laboratory
• Lynn Cominsky, Education and Outreach Lead, Sonoma State University
• Karl Forster, Science Operations Center Manager, California Institute of Technology
• Charles Hailey, Optics Lead, Columbia University
• Vicky Kaspi, Galactic Science Team Lead, McGill University
• David Oberg, Spacecraft Bus Program Manager, Orbital Sciences Corporation
• Daniel Stern, Project Scientist, Jet Propulsion Laboratory
• Jason Willis, Project Systems Engineer, Jet Propulsion Laboratory
• William Zhang, Goddard Optics Lead, Goddard Space Flight Center

The science team includes researchers from more than 20 additional institutions worldwide, including Durham University and Stanford University/ KIPAC.

And now, the mission particulars...

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley (UC Berkley); Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; and ATK Aerospace Systems, Goleta, California. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. For more information on the NuSTAR mission, visit www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .

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Happy 45th, Explorer 35!

The above image, taken in July 1967, shows NASA's Explorer 35 spacecraft being prepared for launch. Image Credit: NASA

This Thursday, July 19th, marks the 45th anniversary of the launch of NASA's lunar orbiter, Explorer 35 (IMP-E). Explorer 35 was the eighth lunar orbiter mission launched from Earth and the fifth launched by the United States. Unlike the U.S. Lunar Orbiter missions, which performed photo reconnaissance to prepare for U.S. human landings on the moon, the focus of the Explorer 35 mission was interplanetary study. Its mission disciplines included planetary science, solar physics and space physics.

The Explorer 35 spacecraft was spin-stabilized and instrumented for interplanetary studies, at lunar distances, of the interplanetary plasma, magnetic field, energetic particles, and solar X-rays. The spacecraft was launched into an elliptical lunar orbit. The spin axis direction was nearly perpendicular to the ecliptic plane, and the spin rate was 25.6 rpm. Explorer 35 achieved all of its mission objectives and, after successful operation for 6 years, was turned off on June 24, 1973.

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Cast Your Vote for the Next Discovery Mission!

The above image shows three possible NASA missions. On the left, the InSight mission is designed to map the structure of Mars. (Image Credit: JPL/NASA) In the center, the TiME mission would float on a hydrocarbon sea on Titan. (Image Credit: Johns Hopkins Univ. Applied Physics Laboratory/Lockheed Martin) On the right, the Chopper mission seeks to study a comet in depth. (Image Credit: NASA/GSFC/University of Maryland)

On July 11th, the journal Nature published online an article, by Eric Hand, reviewing the three finalists for NASA's next low-cost mission to our solar system. If you have not read it yet, I encourage you check it out.

Very soon, NASA's Discovery Program will award one of these mission proposals with $425 USD to further the study of Mars, Titan, or comets. But which proposal should get the green light? Here is a brief rundown of each.

InSight

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission would map out the deep structure of Mars by listening to its faint, visceral rumblings. The mission would borrow its design from the 2007 Phoenix lander, which proved that Discovery-budget Mars lander missions were possible. InSight would land in 2016 at Elysium Planitia, a large, relatively smooth area near the Martian equator, with lots of sunlight for a solar-powered mission. A sensitive seismometer would be plunged into the surface and seek to better understand the internal structure of Mars and how it developed. The InSight mission proposal is led by Bruce Banerdt of NASA's Jet Propulsion Laboratory in Pasadena, California.

TiME

The Titan Mare Explorer (TiME) mission would take a 1.5-hour parachute descent to the surface of Ligeia Mare, a hydrocarbon sea near the north pole of Titan that is larger than North America's Lake Superior. TiME would then drift freely and study the Titan weather and sea. NASA’s current mission to the Saturn system, Cassini, has already observed hydrocarbons such as methane and ethane on Titan, and delivered the Huygens probe to briefly study the surface. But a spectrometer on TiME will be able to study the hydrocarbon soup in detail, looking for signs of a complex prebiotic chemistry. The TiME mission proposal is led by Ellen Stofan of Proxemy Research in Laytonsville, Maryland.

Chopper

The Comet Hopper (Chopper) mission would rendezvous in 2012 with the 1.2-kilometer-wide Comet 46P/Wirtanen and spend then spend at least two years tagging along. Chopper would meet 46P/Wirtanen at roughtly the distance of Jupiter's orbit, then watch as it hurtled toward the sun and develop its effervescent coma. Twelve times during the mission, chopper would gently land on the comet and stick sensors into the surface to study the comet's composition. Identifying the physical and chemical processes of the comet could reveal whether the variation between comets reflects conditions of the primoridal outer solar system, which was previously thought to be relatively uniform. The Chopper mission proposal is led by Jessica Sunshine, a planetary scientist at the University of Maryland in College Park.

Take the Poll

Of course, the final decision on the proposal winner rests with NASA. But you at least have a chance to give your opinion on the choice. The Nature article includes a poll in which you may select your preference from the three finalists. So don't wait! Vote now! CLICK HERE to read the Nature article and cast your vote.

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NuSTAR: Telescope Overview, Part 2

The above image shows one of two optics units which make up NuSTAR's telescope. Image Credit: NASA/JPL-Caltech

We now continue our overview of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, which launched June 13th. Here is part two of the telescope overview.

The Telescope, Continued

Detectors

To register the image focused by the optics, NuSTAR requires high-energy X-ray detectors capable of measuring the position and energy of the incoming X-rays. In this case, the detectors are called focal-plane detectors because they reside where light from the telescope is focused. The detectors electronically register each X-ray interaction, building up an image over time. Similar to the digital detectors used in cell-phone cameras, these detectors are made of a crystalline material divided up into pixels, which absorb X-rays and in the process create an electronic signal. The challenge in making the NuSTAR detectors was to find a material dense enough and with the right properties to block penetrating high-energy X-rays. Further, very sensitive electronics had to be custom designed to accurately measure the tiny signals produced by X-ray interactions.

NuSTAR’s focal-plane detectors are manufactured from crystals of cadmium-zinc-telluride, a semiconductor material with the ability to stop high-energy X-rays. The detectors are printed with a 32 by 32 pattern of pixels. Each pixel is connected to an input on a low-noise readout chip designed for NuSTAR by the Caltech team. The readout chip measures the X-ray energy to better than one part in 60, which is important for looking for signatures of radioactivity in the remnants of exploded stars. Four of these detectors are placed in a two-by-two array to make up the 64 by 64 pixel focal plane.

The focal plane detectors are shielded by a well of material that is itself a particle and X-ray detector. These shields register high-energy photons and cosmic rays that impact the focal plane from directions other than along the NuSTAR optical axis. Such events are the primary background for NuSTAR and must be properly identified and subtracted to identify high-energy photons from cosmic sources. NuSTAR rejects background X-rays by ignoring any signal from a detector that occurs at the exact same time a background event is recorded on the shield.

The optics and detector technologies were successfully tested on a balloon-borne experiment, called the High Energy Focusing Telescope, in 2005. Fiona Harrison, the principal investigator of NuSTAR, was also the principal investigator of that project. Collaborating institutions were NASA, Caltech, Columbia University, the Danish Technical University and the Lawrence Livermore National Laboratory in Livermore, California.

The Mast

Bridging the mirrors and the detectors is a mast, a little over 33 feet (10 meters) long. Because X-rays graze off the mirrors at nearly parallel angles, X-ray telescopes require long focal lengths (the distance between the optics and the detectors, or focal plane). NASA’s Chandra X-ray Observatory, which also has a 33-foot (10-meter) focal length, accomplishes this with a large, fixed structure, which required the space shuttle to launch. But NuSTAR is a NASA Small Explorer mission that must launch on a compact, low-cost rocket. The solution is an extendable mast, which is stowed in a canister approximately 3.3-feet (one-meter) tall during launch. About a week after launch, the mast will unfold, driven out by a motor in a process that takes about 25 minutes.

The articulated mast, built by ATK Aerospace Systems, Goleta, Calif., is based on a design used to establish a 197-foot (60-meter) separation between the two antennae of the Shuttle Radar Topography Mission (SRT M), which flew on the Space Shuttle Endeavour in February 2000 and made high-resolution elevation (topographic) maps of most of our planet. The mast is low weight, compact and provides a stiff and stable structure connecting the precisely aligned benches.

After the mast is deployed in space, scientists will check that the optics units and focal plane detectors are properly aligned. An adjustment mechanism is built into the mast, which allows for the alignment of the optics bench to be precisely altered if needed.

Laser Metrology System

Tiny changes in the position of the mast will also occur throughout the mission. The structure is not perfectly rigid and undergoes slight thermal distortions, particularly when going in and out of Earth shadow.

A laser metrology system will measure changes in the relative position of the optics bench and the focal plane via two lasers mounted on the optics bench that are paired with two position-sensitive detectors mounted on the focal plane. A star-tracker device on the optics bench provides additional angular information. These data will be used to correct for the small mast movements during image processing on the ground.

And now, the mission particulars...

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley (UC Berkley); Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; and ATK Aerospace Systems, Goleta, California. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. For more information on the NuSTAR mission, visit www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .

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NuSTAR: Telescope Overview

The above image is a chart explaining the spectrum of electromagnetic radiation (EMR). The NuSTAR mission examines the universe in the High-energy X-ray band of the EMR. Image Credit: NASA/JPL-Caltech

We now continue our review of NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, which launched June 13th. In this outing, we focus (pun intended) on the telescope itself and the X-rays it observes...

Seeing With X-Ray Eyes

Doctors use high-energy X-rays to see through your skin and take pictures of your bones, and fictional superheroes like Superman use X-ray vision to see through buildings. High-energy X-rays, which have much shorter wavelengths than visible-light photons, can penetrate certain materials. The same is true in the cosmos. High-energy X-rays can travel through gas and dust, so telescopes with high-energy X-ray eyes can see behind walls of obscuring material.

X-rays cannot, however, penetrate our atmosphere because it is actually quite thick. As a result, X-ray telescopes must operate from space.

What types of objects emit X-rays? The hottest, densest and most energetic objects in the universe glow with X-rays. The hotter the object, the more light it radiates at higher energies. Our bodies, for example, have temperatures of hundreds of kelvins (about 98 degrees Fahrenheit), and glow with lower-energy infrared light we can’t see with our eyes. The surface of our sun has a temperature of 6,000 kelvins (approximately 10,000 degrees Fahrenheit) and is glowing predominantly with visible light. Feeding black holes, supernova remnants and other objects with temperatures of millions of kelvins (degrees Fahrenheit) shine with X-rays. It is these objects that NuSTAR will study.

The Telescope

Since Galileo’s first homemade telescope in 1609, astronomers have been using mirrors and lenses to focus light and study the cosmos. X-rays are a form of light like the visible light we see with our eyes, but they have wavelengths about the size of an atom, or 10,000 times smaller than that of visible light. X-rays interact with matter and reflect off surfaces very differently than visible light.

As a result, focusing X-ray light requires a different type of design than traditional telescopes. Most of the designs in use for astronomical telescopes are based on variations of the same basic “reflector geometry,” first invented by Hans Wolter in 1952. As explained below, this technology exploits the fact that more X-rays can be reflected when they hit surfaces at very small, glancing angles.

Telescopes operating in the low-energy part of the X-ray band have flown on numerous missions, but until now, no space telescope has focused high-energy X-rays into sharp images. Over the last decade, the technologies behind high-energy X-ray telescopes have seen significant breakthroughs, with NuSTAR’s design being at the forefront, and the first to be launched into orbit.

The NuSTAR telescope consists of three main parts: the optics, or mirrors, which focus the light; the detectors, which record the image; and an extendable mast, which holds the optics and detectors at the required 33-foot (10-meter) separation distance once in orbit. NuSTAR has two optics units aligned to look at the same location on the sky. The two sets of images are added together on the ground to see fainter objects.

NuSTAR will detect high-energy X-rays with energies ranging from 5 to 80 keV, or kilo electron volts (keV). For reference, NASA’s Chandra X-ray Observatory detects low-energy X-rays between 0.1 and 10 keV.

Optics

X-rays don’t behave like visible light. They have much higher energies and only reflect off surfaces at glancing angles, like stones skipping off the surface of a lake. While visible light can reflect off a mirror at essentially any angle, an X-ray hitting a flat surface head-on will be absorbed.

Telescope designs that focus X-rays must therefore use mirrors that are nearly parallel to the incoming X-ray beam. This is accomplished with conical mirrors. An individual mirror has two near-conical sections — a front and a back — so that X-rays reflect twice before heading toward the focal plane, where the light is focused. The two reflections are required to remove distortions that would otherwise arise in the image.

A single mirror by itself will only intercept a small amount of light because its surface is nearly parallel to the incoming beam of radiation. To increase the collecting area, X-ray telescopes use multiple mirrors, often called shells, with different sizes, nested inside each other. Each shell’s surface has a slightly different angle relative to the incoming radiation, so that they all focus X-rays to the same spot on the focal plane.

This type of design, called grazing-incidence X-ray optics, has been used on previous low-energy X-ray missions, including NASA’s Chandra X-ray Observatory. The challenge faced by NuSTAR is to extend these optics to higher energies, which require even smaller, or more glancing, reflecting angles. Because the surfaces must be almost parallel to the beam, many more reflectors are needed. They must also be thin so they don’t block too much light. The Chandra mirror has four shells, each between 0.8 to 1.2 inches (2 to 3 centimeters) thick, whereas NuSTAR requires 133 shells that are 0.008 inch (0.02 centimeter) thick — about the thickness of a fingernail.

To efficiently reflect the light in NuSTAR’s energy range, specialized coatings are deposited on the reflecting surfaces. These coatings, similar to anti-reflective coatings on sunglasses, consist of hundreds of thin films alternating between light and dense materials. While coatings on sunglasses reduce reflections, NuSTAR’s coatings are designed to enhance them. Each film in the coatings is just a few atoms thick.

To manufacture NuSTAR’s optics, very thin, smooth glass segments were formed, coated with the specialized films and mounted into two optic modules. Each shell, or layer, is made up of between 12 and 24 pieces.The curved pieces were carefully crafted at NASA’s Goddard Space Flight Center in Greenbelt, Md. Flexible, thin glass just like that found in laptop and cell phone screens, was shaped by placing it over molds, and then heated in ovens to temperatures of 1,100 degrees Fahrenheit (593 Celsius). As the glass was heated, it bent to the appropriate rounded shape. More than 9,000 individual mirror segments were created for NuSTAR’s nested mirrors.

The reflective coatings, consisting of alternating layers of platinum and carbon, or tungsten and silicon (depending on the shell) were applied in a specially designed vacuum chamber at the Danish Technical University Space Centre in Denmark. The complex, tightly nested arrangement of mirror pieces was assembled at Columbia University’s Nevis Laboratory just outside New York, N.Y. Starting from the inside out, each piece was carefully added to a growing barrel, spaced apart by graphite and held together by epoxy. To be continued...

And now, the mission particulars...

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley (UC Berkley); Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; and ATK Aerospace Systems, Goleta, California. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. For more information on the NuSTAR mission, visit www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .

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AR 1520-1521 Solar Flare and CME of July 17th

The above X-ray image was taken July 18th 02:44 UTC (July 17th 10:44 PM EDT) by the GOES 15 satellite. The X-ray emissions from AR 1520 and AR 1521 may be seen at the lower right (approaching the sun's western limb). This region was was the source of the M1.8-class solar flare and coronal mass ejection of July 17th. Image Credit: NOAA 

On July 17th at 17:15 UTC (1:15 PM EDT) the sunspot complex AR 1520-1521 (a combination of Active Regions 1520 and 1521) erupted with an M1.8-class X-ray solar flare which unfolded slowly over a few hours. Slow eruptions often produce coronal mass ejections (CMEs) and this one did not disappoint. The CME is expected to pass the planet Venus on July 19th and could give a glancing blow to Earth on July 20th. CLICK HERE to view a movie of the July 17th eruption, made by the Solar and Heliospheric Observatory (SOHO).

Meanwhile back a home, Earth's magnetic field is still settling down from the CME which passed on 14th. The odds of observing more aurorae over the evening of July 17th-18th are slim, but not out of the question.

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: http://www.swpc.noaa.gov/ .

To learn more about the sun and to stay current on solar activity, visit the mission home pages of the Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov and the Solar and Heliospheric Observatory (SOHO), sohowww.nascom.nasa.gov .

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NuSTAR: Spacecraft Overview

The above image shows the NuSTAR observatory (in stowed configuration) with components labeled. Image Credit: NASA/JPL-Caltech

Back on June 13th, NASA launched its Nuclear Spectroscopic Telescope Array (NuSTAR) atop a three-stage Pegasus XL rocket. On June 22nd, NuSTAR's mast was unfurled in order to position its stereo optics. And on June 28th, NuSTAR experienced "first light," imaging the black hole Cygnus X-1 in the constellation Cygnus. Normal science operations were expected to commence about 30 days after launch. Nothing more has been released to-date. But while we wait, I thought we could advantage of the time and get to know the the mission and the orbiting observatory in greater detail. Here is a overview of the observatory itself...

The Spacecraft

The integrated NuSTAR observatory consists of a single science instrument rigidly mounted to a spacecraft infrastructure, or bus, containing the avionics, power and attitude (pointing) control systems. The science instrument itself is made up of two benches, one for the optics and one for the focal plane. At launch, the benches are mounted on either end of a canister that contains the folded-up mast. These two benches are coupled during launch, separation and initial checkout. The benches are separated by non-explosive actuators and as the mast deploys, unfolding out of its canister, the two benches move apart until the mast is fully deployed and latches into place.

In its stowed-for-launch configuration, the observatory is compact and approximately 3.7 feet (1.1 meters) in diameter and 6.3-feet (1.9-meters) tall; these dimensions are driven by the need to fit within the fairing of the Pegasus launch vehicle. In its deployed configuration after reaching orbit and extending the mast, the observatory is 37.3-feet (11.4-meters) long, or approximately the length of a school bus.

Spacecraft Bus (and Focal Plane Bench)

The spacecraft bus (which contains the focal plane bench) has an aluminum honeycomb sandwich structure, and weighs 380 pounds (173 kilograms). The spacecraft bus is a compact structure 3.3 by 3.7 by 1.8 feet (1.0 by 1.1 by 0.5 meters). The bus provides all of the usual spaceflight capabilities in its respective subsystems: radio frequency communications, electrical power, command and data handling, attitude control, thermal control, and mechanical, electrical and thermal support to the instrument. The bus also provides the mechanical and electrical interfaces to the launch vehicle.

The spacecraft was built by Orbital Sciences Corporation, and its design is based on the company’s LEOStar-2 bus.

Attitude Control and Determination Subsystem

The NuSTAR observatory’s attitude control subsystem is a three-axis stabilized zero-momentum system. It utilizes reaction wheels combined with torque rods for attitude control. The attitude determination system is based around the Danish Technical University microASC star tracker supported by an Inertial Reference Unit (gyroscope), a magnetometer and several coarse sun sensors.

Command and Data Handling Subsystem

The spacecraft Command and Data Handling subsystem consists of three processors — the OnBoard Computer and the Uplink Card in the Central Electronics Unit, and the Attitude and Power Electronics microcontroller. The Command and Data Handling system provides control over all spacecraft functions including commanding (real-time and stored commands), payload data storage and playback, housekeeping data storage/playback, power subsystem management support, thermal subsystem management support, attitude control and instrument interface control.

Downlink of real-time and stored spacecraft bus and instrument housekeeping telemetry is handled via the Downlink Card in the Central Electronics Unit, along with the high-rate science playback data from the instrument.

Electrical Power Subsystem

The power system consists of a direct energy transfer system utilizing a solar array with a surface area of 29 square feet (2.7 square meters) capable of generating 729 watts of power. For power storage, NuSTAR has two lithium-ion batteries with a total capacity of 48 amp-hours.

Communications Subsystem

Communications with the ground is accomplished via an S-band communications subsystem and two omnidirectional antennae, compatible with the Italian Space Agency’s tracking station in Malindi, Kenya, as well as with NASA’s Tracking and Data Relay Satellite System for critical event coverage. The antenna configuration and coverage allows for commanding in all attitudes and downlink in most attitudes. The S-band communications subsystem has a redundant receiver.

Thermal Control Subsystem

The thermal control subsystem consists of passive elements (multilayer insulation blankets and radiator panels) and heaters. It protects the spacecraft by maintaining the temperatures within the flight-allowable limits.

There. Now you are up to speed on the observatory/spacecraft in general. We will go into more detail soon...

Throughout its two-year prime mission, NuSTAR will turn its focused gaze on the most energetic objects in the universe, producing images with 100 times the sensitivity and 10 times the resolution of its predecessors operating at similar wavelength ranges. It will take a census of black holes both inside and outside of our Milky Way galaxy, and answer questions about how this enigmatic cosmic "species" behaves and evolves. Because it sees high-energy X-rays, NuSTAR will also probe farther into the dynamic regions around black holes, where matter is heated to temperatures as high as hundreds of millions of degrees, and will measure how fast black holes are spinning.

Other targets for the mission include the burnt-out remains of dead stars, such as those that exploded as supernovae; high-speed jets; the temperamental surface of our sun; and the structures where galaxies cluster together like mega-cities.

And now, the mission particulars...

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley (UC Berkley); Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; and ATK Aerospace Systems, Goleta, California. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. For more information on the NuSTAR mission, visit www.nasa.gov/nustar and www.nustar.caltech.edu/ .

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Sun Relatively Quiet for July 17th

The above image was taken July 16th by the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO). HMI captures images at 6173 Angtroms with a resolution of 1 arcsecond. Image Credit: SDO/HMI/GSFC/NASA 

After several postings of the sun in the X-ray, Hydrogen-Alpha, and various other bands of the electromagnetic spectrum, we thought it might be nice to see the sun in something close to a heavily filtered perspective. So we chose this image taken July 16th by the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO). Granted that you don't get as much visual information as those other bands might provide, you do get a good view of the sunspots. Or should we say, the human-eye visible manifestations of the active regions of the sun? Oh, well. Look at the pretty sunspots...

NOAA's Space Weather Prediction Center reports that solar activity continues to be low, but there continues to be a chance for an isolated M-class solar flare activity. Active Region AR 1520 is the most likely source. A decline in activity by July 19th as regions AR 1519, 1520, and 1521 cross the western limb and disappear from sight.

Earth's geomagnetic activity is expected to be unsettled with a chance for activity on July 17th. In addition, there is a chance for isolated minor to major storm periods at high latitudes during the earlier part of the 17th. Solar wind driving of the magnetosphere is expected to continue to decrease in intensity throughout the day and predominantly quiet levels are expected for July 18th and 19th.

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: http://www.swpc.noaa.gov/ .

To learn more about the sun and to stay current on solar activity, visit the mission home page of the Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov .

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MESSENGER: 1,000+ Orbits and Counting…

The above image was released December 1, 2011 by the NASA MESSENGER mission. It shows an orthographic projection of a global mosaic of the planet Mercury, centered at 0°N, 270°E. Beethoven basin is visible towards the southwest. Kuiper crater appears brighter than its surroundings towards the eastern edge near the equator. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington 

Back on June 22nd, NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission completed its 1,000th orbit of the planet Mercury.

The MESSENGER spacecraft entered orbit around Mercury in mid-March of 2011, after traveling more than 15 times around the sun through the inner solar system and completing six planetary flybys. That means it took just over 15 months to reach this milestone. Of course, the orbits are fast because MESSENGER is so close to Mercury, and its going to get closer. In April, the period was reduced from 12 hours to 8 hours, so it will take MESSENGER only 11 months to complete the next 1,000 orbits.

During MESSENGER’s primary mission, which concluded on March 17th, the spacecraft and mission team performed the first global reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of Mercury. The spacecraft is now one-third of the way into a one-year extended mission that is building on this knowledge to address new questions raised by the initial orbital observations.

The mission team is very proud of their little orbiter, having to constantly endure high temperatures and increasingly frequent streams of solar energetic particles. And with the primary mission completed successfully, the team members look forward to the new science that MESSENGER will glean from the closest planet in our solar system.

For example, in the first week of May, MESSENGER’s Mercury Dual Imaging System (MDIS) delivered the 100,000th image of Mercury since arrival. MDIS — one of seven instruments aboard the spacecraft — has globally mapped the planet in high-resolution monochrome images and in color images through eight of its color filters, uncovering a new view of Mercury and shedding light on the planet's geologic history.

We extend our hearty congratulations to the great achievements of MESSENGER. We salute the spacecraft and mission team, and we look forward to the discoveries to come.

And now, the mission particulars…

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER’s extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA. To learn more about Mercury and MESSENGER, visit messenger.jhuapl.edu .

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Already Dreaming of the Next Model...

The above image provides an overview of the entry descent and landing stages for NASA's Mars Science Laboratory / Curiosity mission, planned to touch down on August 5th. Image Credit: NASA/JPL-Caltech

NASA's Mars Science Laboratory (MSL) Curiosity mission is set to land on the Red Planet August 5th. But even before the rover's odometer has begun to tick over, NASA's planners are already dreaming about the next model to come off the line.

The director of NASA's Mars Exploration Program (MEP), Doug McCuistion, was in the UK on July 10th for the 2012 Farnborough International Airshow. At the event, McCuistion speculated on the requirements of the next mission that would be designed from the ground up for Mars. The following is a general rundown of McCuistion's remarks at the event.

The future Mars mission must be cheaper than MSL/Curiosity, which is costing $2.5 billion. The future mission would cost no more than $800 million (about the budget of a NASA Discovery mission).

The mission should launch by 2018 to 2020. It would also feature larger parachutes, to help slow the spacecraft during entry. It would have at least one atomic clock to improve its landing accuracy. Also, it would have inflatable decelerators, also known as ballutes, to cushion the craft at touch-down (so it seems we are back to bouncing). The upshot is that with these noted items, mission controllers would be able to reduce the size of the landing ellipse, or increase the accuracy of the landing.

But even with the cost-cutting measures, McCuistion expects the mission to be viable and produce lots of good science, though he did note that lower-budget missions tended to be characterized by simpler systems that were not as challenging.

But low budget does not necessarily mean small craft. For example, McCuistion would like to move from the 69-foot (21-meter) chutes used by the Viking landers to new, 98-foot (30-meter) ones that are capable of producing more drag, and depositing a larger payload safely on the Martian surface.

This future Mars mission could come in the form of a rover (like Mars Exploration Rover Spirit or Opportunity) or a lander (like the 2008 Phoenix Mars Lander mission).

Finally, McCuistion added that the NASA Office of the Chief Technologist might have to finance the ballutes, the new parachutes, and the atomic clocks, since the MEP will most likely be strapped for cash for the foreseeable future.

Already in the pipeline is NASA's Mars Atmosphere Volatile Evolution (MAVEN) spacecraft, which is scheduled to launch in late 2013 and enter orbit around Mars in late 2014 or early 2015. The primary objective of MAVEN is to learn more about the Martian atmosphere, including the source of its methane.

And now, the program particulars...

NASA's Mars Exploration Program (MEP) is a science-driven program that seeks to understand whether Mars was, is, or can be, a habitable world. To find out, scientists are working to understand how geologic, climatic, and other processes have worked to shape Mars and its environment over time, as well as how they interact today.

The four science goals for MEP are: (1) Determine if life ever arose on Mars; (2) Characterize the climate of Mars; (3) Characterize the geology of Mars; and (4) Prepare for human exploration of Mars. To learn more, visit www.nasa.gov/mars and mars.jpl.nasa.gov .

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Farewell to the AR 1520 CME Aurorae?

The above X-ray image was taken July 16th 12:04 UTC (8:04 AM EDT) by the GOES 15 satellite. The X-ray emissions from AR 1520 and AR 1521 may be seen at the lower right (approaching the sun's western limb). Image Credit: NOAA 


Following the July 14th passage of the coronal mass ejection (CME) produced by the sun's Active Region 1520 (AR 1520), the geomagnetic turmoil is beginning to wane. But the evening of July 14th to 15th saw some good aurora activity. In North America alone, aurorae were observed as far south as Oregon, Colorado, Missouri, Utah, Wisconsin, Iowa, Minnesota, Washington, Illinois, Kansas, South Dakota, Nebraska, Michigan and Arkansas. According to NOAA's Space Weather Prediction Center, Earth's geomagnetic field is expected to be at quiet-to-active levels on July 16th, and a to return to predominantly quiet levels is expected for July 17th. Even so, observers should be on the watch for lingering aurorae over the night of July 16th to 15th.

Meanwhile, back on the sun... Activity through July 18th is expected to be at low levels with a 40% chance of M-class solar flares. X-class flares are also possible, but very low, at 15%. Regions AR 1520 and AR 1521 are continuing their rotation toward the sun's western limb. We'll wait and see if they have any more surprises for us before the make their exit. Stay tuned...

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: http://www.swpc.noaa.gov/ .

To learn more about the sun and to stay current on solar activity, visit the mission home page of the Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov .

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Odyssey in Safe Mode 21 Hours July 11-12

The above image is an artist's concept of NASA's Mars Odyssey spacecraft orbiting the planet Mars. Odyssey has been orbiting Mars since October 24, 2001. Image Credit: NASA/JPL-Caltech

NASA continues careful study of its Mars Odyssey orbiter following the events of June. At that time, Odyssey put itself into safe mode (reduced activity, pointed at Earth, and awaited instructions) because of issues with one of its three reaction control wheels. The wheels are used for most of Odyssey’s attitude adjustments, saving the thrusters and their propellant for more important uses. Engineers were able to resolve the problem by decommissioning the glitchy wheel and putting into service a spare wheel which was included in the spacecraft design for just that purpose. Following that, engineers began careful monitoring to be certain that Odyssey (along with NASA’s Mars Reconnaissance Orbiter) can support NASA’s Mars Science Laboratory / Curiosity rover mission, which will land early August.

On July 11th, Odyssey hit a small pothole on the road to recovery. At about 1:00 PM EDT (10:00 AM PDT) Odyssey performed a planned 1.5-second thruster burn for an orbit-trim maneuver. Interestingly, it was the shortest-duration burn since Odyssey’s arrival at Mars a decade earlier. It seems the burn put unanticipated strain one of the three reaction control wheels — possibly that newly activated wheel, but NASA’s report does not make that clear. In any case, Odyssey followed its rules and put itself into safe mode (reduce activity, point at Earth, and await instructions). Fortunately for the mission engineers, Odyssey did not reboot during the hiccup, so they were able to review Odyssey’s diagnostic information and understand what happened and why.

On July 12th, 21 hours after Odyssey initiated safe mode, engineers reoriented the spacecraft toward the Martian surface and began to gradually bring Odyssey back up to normal spacecraft activities. Engineers will be assessing whether another orbit-trim maneuver is warranted.

And now, the mission particulars...

Since its arrival October 2001, the Mars Odyssey orbiter has worked at Mars for more than 10 years, which is longer than any other Mars mission in history. Besides conducting its own scientific observations, it serves as a communication relay for robots on the Martian surface. Odyssey is managed by NASA's Jet Propulsion Laboratory (JPL), Pasadena, for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver built the spacecraft. JPL and Lockheed Martin collaborate on operating the spacecraft. For more about the Mars Odyssey mission, visit: mars.jpl.nasa.gov/odyssey .

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Catch AR 1520 CME Aurorae Before They're Gone!

The above image is an overview of the current aurora activity over the north pole (left) and south pole (right) as of today (July 15th) at 23:59 UTC (7:59 PM EDT). The images are extrapolated from measurements taken during the most recent polar pass of the NOAA POES satellite. Image Credit: NOAA/Space Weather Prediction Center 

Currently in progress is the geomagnetic storm caused by the passing of the July 12th coronal mass ejection (CME) from the sun's Active Region 1520 (AR 1520). NOAA/National Weather Service reports the geomagnetic storm activity continues to be (G2). 

Over the evening of July 14th to 15th, the aurora borealis (northern lights) appeared in the United States as far south as California, Colorado, Missouri, Utah, Wisconsin, Iowa, Minnesota, Washington, Illinois, Kansas, Nebraska, Michigan and Arkansas.

So far for the evening of July 15th to 16th, aurorae have been reported in the northern hemisphere from observers in Scandinavia, Canada and Alaska. In the southern hemisphere, the aurora australis (southern lights) has been sighted in New Zealand, Australia, and directly above the South Pole itself.

In North America, northern-tier U.S. states from Maine to Washington, and all points northward, should be alert for aurorae after nightfall. Observers, please note that the best hours for aurora-spotting are around local midnight.

Meanwhile, back on the sun... No significant activity is reported from AR 1520 or AR 1521. These regions continue to rotate toward the sun's western limb. There is the potential for more activity from these regions, but nothing major at the moment. Stay tuned...


To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov/today.html . 

To learn more about the sun and to stay current on solar activity, visit the mission home page of the Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov . 

To catch postings for all my blogs, subscribe on Twitter to twitter.com/RoamingAstro . Email feedback to: RoamingAstroInput@gmail.com . 

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AR 1520 CME Aurorae Abound!

The above image is an overview of the current aurora activity over the north pole (left) and south pole (right) as of today (July 15th) at 11:29 UTC (7:29 AM EDT). The images are extrapolated from measurements taken during the most recent polar pass of the NOAA POES satellite. Image Credit: NOAA/Space Weather Prediction Center 

As of Sunday, July 15th, NOAA/National Weather Service reports the geomagnetic storm activity to have risen to moderate (G2) as a result of the ongoing coronal mass ejection (CME) produced from the sun's Active Region AR 1520 on July 12th. No further significant activity has occured, and while AR 1520 has become less of a threat, it still has the potential for further activity. Stay tuned... 

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov/today.html . 

To learn more about the sun and to stay current on solar activity, visit the mission home page of Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov . 

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Two Lunar Occultations for July 15th

The above image of asteroid 21 Lutetia was taken July 11, 2010 by the Rosetta spacecraft. Image Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

It seems our moon has a busy schedule this morning, July 15th. It has the brashness to achieve not one, but two occultations of note. And depending where you are, you might be able to catch one or both of them. Please read on.

Occultation One

On Saturday, July 15th, people in Europe and northern Asia have an opportunity to observe a lunar occultation of the planet Jupiter. The event is expected to begin about 00:54 UTC, reach mid-point at 03:07 UTC, and then conclude at 05:09 UTC. Jupiter is currently in the constellation Taurus, the Bull, not far from the red star Aldebaran, and shining at magnitude -2.1. The planet Venus is also nearby, adding to the spectacle. For more details on the lunar occultation of Jupiter, click here to visit the online information page provided by the U.S. Naval Observatory.

Occultation Two

At roughly the same time, people in the Arctic Circle have the opportunity to observe a lunar occultation of asteroid 21 Lutetia. The event is expected to begin about 04:38 UTC, reach mid-point at 06:29 UTC, and then conclude at 08:05 UTC. 21 Lutetia is a large main-belt asteroid, measuring about 100 kilometers in diameter (120 km along its major axis). It was discovered in 1852 by German-French astronomer and painter Hermann Goldschmidt, and is named after Lutetia, the Latin name of the city that stood where Paris was later built.

Lutetia has an irregular shape and is heavily cratered, with the largest impact crater reaching 45 km in diameter. The surface is geologically heterogeneous and is intersected by a system of grooves and scarps, which are thought to be fractures. It has a high average density, meaning that it is made of metal-rich rock.

The ESA's Rosetta spacecraft passed within 3,162 km (1,965 mi) of Lutetia in July 2010. It was the largest asteroid visited by a spacecraft until the NASA's Dawn mission arrived at 4 Vesta in July 2011.

For more details on the lunar occultation of 21 Lutetia, click here to visit the online information page provided by the U.S. Naval Observatory.

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It's AR 1520 Aurora Time!

The above X-ray image was taken 00:52 UTC (8:52 PM EDT) by the GOES 15 satellite. The X-ray emissions from AR 1520 and AR 1521 may be seen at the lower right (western limb). Image Credit: NOAA 


It is growing dark on the east coast of North America, so time for those folks to start looking for aurorae. Folks in the eastern hemisphere should already be on the lookout.

Today (July 14th) at about 18:00 UTC (2:00 PM EDT) the corona mass ejection (CME) from July 12th passed Earth's atmosphere. According to NOAA/National Weather Service, a minor (G1) geomagnetic storm is underway and should continue through the weekend, with a chance that it might grow to moderate (G2) levels. Be on the lookout for aurorae over the evenings of July 14th and July 15th.

Back on the sun, solar activity is moderate, as Active Regions AR 1520 and AR 1521 continue to rotate toward the western limb. Stay tuned...

To see other July 12th images as well as a SDO video of the flare, visit the NASA news release here, www.nasa.gov/mission_pages/sunearth/news/News071212-X1.4flare.html . 

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov/today.html . 

To learn more about the sun and to stay current on solar activity, visit the mission home page of Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov . 

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Awaiting AR 1520 CME, Sun Quiet

The above X-ray image of the sun was taken by the GOES 15 satellite. Image Credit: NOAA

The sun is reasonably quiet as Earth awaits the passage of the coronal mass ejection (CME) which was produced during the X1.4 solar flare on July 12th. NOAA's Space Weather Prediction Center expects geomagnetic storm activity to be minor (G1) to moderate (G2) after 9:00 AM EDT (13:00 UTC). Also, a minor (S1) solar radiation storm continues to linger in the wake of the July 12th flare. Stay tuned...

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov/today.html .

To learn more about the sun and to stay current on solar activity, visit the mission home page of Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov .

To catch postings for all my blogs, subscribe on Twitter to twitter.com/RoamingAstro . Like what you see? Let me know! Email: RoamingAstroInput@gmail.com .

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2007 LE and 5143 Heracles are BOTH Binaries!

The above image shows the William E. Gordon Telescope, the radio telescope at Arecibo Observatory, National Astronomy and Ionosphere Center. Observations taken at Arecibo in December 2011 showed astronomers that 5143 Heracles was a binary system. Image Credit: NOAA  

It's a minor planet double header! On Friday, July 13th, two discovery teams announced that the asteroid each was studying was in fact a binary asteroid system. Below are the details on each discovery.

2007 LE

Report CBET 3175: M. Brozovic and L. A. M. Benner of the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech); P. A. Taylor, E. S. Howell, and M. C. Nolan of the National Astronomy and Ionosphere Center; J. L. Margot of the University of California, Los Angeles; J. D. Giorgini of JPL, Caltech; M. W. Busch, S. P. Naidu, and C. Nugent, University of California, Los Angeles; C. Magri, University of Maine at Farmington; and M. K. Shepard, Bloomsburg University, report that Goldstone (8560 MHz, 3.5 cm) and Arecibo (2380 MHz, 12.6 cm) delay-Doppler radar images obtained on May 31st through June 5th reveal that minor planet 2007 LE is a binary system. The preliminary size estimates are about 500 m for the primary and about 180 m for the satellite. The orbital separation is at least 800 m, and the discovery team obtained a preliminary estimate for the orbital period of about 13 hours.

5143 Heracles

Report CBET 3176: P. A. Taylor, M. C. Nolan, and E. S. Howell at Arecibo Observatory, National Astronomy and Ionosphere Center (www.naic.edu) report that asteroid 5143 Heracles is a binary system. The team made radar observations in 2011 from December 10th through 13th. The imaging suggest that the component diameters are 3.6 +/- 1.2 km for the primary and 0.6 +/- 0.3 km for the secondary. The orbital period appears to be between 14 and 17 hours with a separation of at least 4 km. The team's report also noted that an orbital period between 40 and 57 hours with an implied separation of at least 11 km could not be ruled out, but would be inconsistent with their assumption of a synchronously rotating secondary body.

The asteroid system 5143 Heracles (1991 VL) was discovered November 7, 1991 from Palomar Observatory by American astronomer Carolyn S. Shoemaker. 5143 Heracles is a near-Earth system, belonging to the Apollo asteroid group. With an orbital period of about 2.48 years, 5143 Heracles is a Mercury grazer and a Mars crosser (perihelion 0.41793075, aphelion 3.24995768 AU). 51430 Heracles has an absolute magnitude of 14.0.

5143 Heracles is named after the son of Zeus and Alcmene in Greek mythology. Heracles was the greatest of the Greek heroes. In Rome and the modern West, he is known as Hercules.

Learn More

To learn more about 2007 LE, 5143 Heracles and other near-Earth objects, check out these URLs:

NASA Jet Propulsion Laboratory (JPL) Small-Body Database Browser, 5143 Heracles (1991 VL), ssd.jpl.nasa.gov/sbdb.cgi?sstr=5143+Heracles .

NASA's Near-Earth Object Program, neo.jpl.nasa.gov .

Information about NASA asteroid missions and activities, www.nasa.gov/asteroids .

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AR 1520 CME Arrival Moved Up!

The above image combines two sets of observations of the sun at 14:45 UTC (10:45 AM EDT) on July 12th from the Solar Dynamics Observatory (SDO) in order to give an impression of what the sun looked like shortly before it unleashed an X1.4 solar flare. The image incorporates light in the 171 Angstrom wavelength (shown in yellow), which shows off giant loops of solar material overlying the middle of the sun over Active Region 1520 (AR 1520) where the flare originated. The second set of observations (in blue) is called a magnetogram, which highlights magnetic fields on the sun. The combined views can help scientists understand the magnetic properties of the sun that lead to giant explosions like flares. Image Credit: NASA/SDO/AIA

Check your tickets. The arrival of the AR 1520 CME has been moved up!

The coronal mass ejection (CME) launched toward Earth by the July 12th X1.4 solar flare is moving faster than originally thought. Analysts at the NASA Goddard Space Weather Lab have revised their forecast accordingly, advancing the cloud's expected arrival time on Saturday, July 14th, to 09:17 UTC (5:17 AM EDT). Weekend auroras are likely.

UPDATE 5:00 PM EDT (21:00 UTC): The NOAA Space Weather Prediction Center is forecasting category G1 (Minor) Geomagnetic Storm activity, with a chance of G2 (Moderate) levels at times through July 15. The S1 (Minor) Solar Radiation Storm persists just above event threshold.

This looks like a good time for a quick refresher on CMEs.

Coronal Mass Ejection Primer

A coronal mass ejection (CME) is a massive burst of solar wind, plasma, and magnetic fields rising above the solar corona or being released into space. CMEs are often associated with other forms of solar activity, most notably solar flares, but a causal relationship between the two has not been established. Most CMEs originate from active regions on Sun's surface, such as groupings of sunspots associated with frequent flares. Near a solar maximum — the period of greatest activity in a solar cycle — the sun produces about three CMEs every day, whereas near a solar minimum — the period of least activity in a solar cycle — there is about one CME every five days.

When a CME reaches Earth, the shock wave causes a geomagnetic storm that may disrupt the Earth's magnetosphere, compressing it on the day side and extending the night-side magnetic tail. When the magnetosphere reconnects on the nightside, it releases power on the order of terawatt scale, which is directed back toward the Earth's upper atmosphere.

This process can cause particularly strong aurorae in large regions around Earth's magnetic poles. These are also known as the Northern Lights (aurora borealis) in the northern hemisphere, and the Southern Lights (aurora australis) in the southern hemisphere. CMEs, along with solar flares, can disrupt radio transmissions and cause damage to satellites and electrical transmission line facilities, resulting in potentially massive and long-lasting power outages.

Humans in space or at high altitudes, for example, in airplanes, risk exposure to intense radiation. Short-term damage may include skin irritation with potential increased risk of developing skin cancer, but it is likely that any affected individuals would recover from any such exposure.

Now, Where Were We?...

As noted earlier, auroras this weekend are likely. Stay tuned...

To see other July 12th images as well as a SDO video of the flare, visit the NASA news release here, www.nasa.gov/mission_pages/sunearth/news/News071212-X1.4flare.html .

To monitor solar flare activity minute by minute, visit the "Today's Space Weather" page of NOAA's Space Weather Prediction Center, URL: www.swpc.noaa.gov/today.html .

To learn more about the sun and to stay current on solar activity, visit the mission home page of Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov .

To catch postings for all my blogs, subscribe on Twitter to twitter.com/RoamingAstro . Like what you see? Let me know! Email: RoamingAstroInput@gmail.com .

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