NuSTAR (SMEX 11, Explorer 93)

NuSTAR (SMEX 11) [NASA]

NuSTAR (Nuclear Spectroscopic Telescope Array) is a X-ray survey mission, which is first satellite to fly a focussing X-ray telescope in space for energies in the 8-80 keV.range.

NuSTAR will survey this energy band for X-ray emission from quasars and Galactic black hole binaries, and obtain spectra of hard X-ray emission from supernova remnants and study the spectral lines created by nuclear transitions which dominate this spectral range.

NuSTAR is a pointed telescope, which was launched by a Pegasus-XL into a low-Earth, equatorial orbit from Kwajalein. The planned mission will last for three years, although less than half that time is required to meet the core science goals. NuSTAR will ordinarily follow a preprogrammed observation plan, but will have the capability of responding to transient opportunities within a day of notification.

The NuSTAR instrument consists of an array of two co-aligned hard X-ray telescopes. The grazing incidence mirrors focus onto two shielded solid-state pixel detectors, separated by a mast that extends the focal length to 10 m after launch. The optics utilize thin glass shells coated with depth-graded multi-layers to extend the bandpass and FOV over that achievable with standard metal surfaces. Cadmium Zinc Telluride (CdZnTe) detectors provide excellent spectral resolution and high quantum efficiency without requiring cryogenic operation. All major elements of the instrument have flight heritage (space flight and HEFT balloon experiment).

The long focal length requires the use of a 10 m extendable mast. The design chosen is produced by Able Engineering, and is a straightforward reduction of the 60 m mast successfully deployed for the SRTM program. A laser metrology system monitors the mast alignment.

A decision on proceeding to flight development with NuSTAR was to be made by early 2006 for a launch in 2008, but it was cancelled in February 2006. In September 2007 NASA restarted the program for a planned launch in early 2012.

The spacecraft was originally to be based on the Spectrum Astro SA-200S bus, but after the restart of the program Orbital was selected to provide a LEOStar-2 based bus. During development, the number of X-ray telescopes in the array was reduced from three to two.