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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