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We present an overview of the NuSTAR non x-ray background. This is dominated by proton scattering in the detector and surrounding material as well as activation lines from of material in the detector and its housing. We also discuss contributions from the solar component (when the Sun is active), and the impact of short-lived radiation belts on the NuSTAR background and activation in the detectors.

Application-specific integrated circuits (ASICs) are used in space-borne instruments for signal processing and detector readout. The electrical interface of these ASICs to frontend printed circuit boards is commonly accomplished with wire bonds. Through silicon via (TSV) technology has been proposed as an alternative interconnect technique that will reduce assembly complexity of ASIC packaging by replacing wire bonding with flip-chip bonding. TSV technology is advantageous in large detector arrays where TSVs enable close detector tiling on all sides. Wafer-level probe card testing of TSV ASICs is frustrated by solder balls introduced onto the ASIC surface for flip-chip bonding that hamper alignment. Therefore, we developed the ASIC test stand (ATS) to enable rapid screening and characterization of individual ASIC die. We successfully demonstrated ATS operation on ASICs originally developed for CdZnTe detectors on the Nuclear Spectroscopic and Telescope Array (NuSTAR) mission that were later modified with TSVs in a via-last process. We tested both backside blind-TSVs and frontside through-TSVs, with results from internal test pulser measurements that demonstrate performance equal to or exceeding the probe card wafer-level testing data. The ATS can easily be expanded or duplicated to parallelize ASIC screening for large area imaging detectors of future space programs.

NuSTAR (the Nuclear Spectroscopic Telescope ARray) is a NASA Small Explorer (SMEX) mission launched in June of 2012. Since its launch, NuSTAR has been the preeminent instrument for spectroscopic analysis of the hard X-ray sky over the 3-80 keV bandpass. The low energy side of the bandpass is limited by the absorption along the photon path as well as by the ability of the pixels to trigger on incident photons. The on-board calibration source does not have a low-energy line that we can use to calibrate this part of the response, so instead we use the "nearest-neighbor" readout in the NuSTAR detector architecture to calibrate the individual pixel thresholds for all 8 flight detectors on both focal plane modules (FPMs). These threshold measurements feed back into the quantum efficiency of the detectors at low (

The Nuclear Spectroscopic Telescope ARray (NuSTAR) has been in orbit for 6 years, and with the calibration data accumulated over that period we have taken a new look at the effective area calibration. The NuSTAR 10-m focal length is achieved using an extendible mast, which flexes due to solar illumination. This results in individual observations sampling a range of off-axis angles rather than a particular off-axis angle. In our new approach, we have split over 50 individual Crab observations into segments at particular off-axis angles. We combine segments from different observations at the same off-axis angle to generate a new set of synthetic spectra, which we use to calibrate the vignetting function of the optics against the canonical Crab spectrum.

The Nuclear Spectroscopic Telescope Array (NuSTAR) launched in June 2012, flies two conical approximation Wolter-I mirrors at the end of a 10.15-m mast. The optics are coated with multilayers of Pt/C and W/Si that operate from 3 to 80 keV. Since the optical path is not shrouded, aperture stops are used to limit the field of view (FoV) from background and sources outside the FoV. However, there is still a sliver of sky (∼1.0 deg to 4.0 deg) where photons may bypass the optics altogether and fall directly on the detector array. We term these photons stray light. Additionally, there are also photons that do not undergo the focused double reflections in the optics, and we term these ghost rays. We present detailed analysis and characterization of these two components and discuss how they impact observations. Finally, we discuss how they could have been prevented and should be in future observatories.

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy (3-79 keV) X-ray observatory operating for four years from low Earth orbit. The X-ray detector arrays are located on the spacecraft bus with the optics modules mounted on a flexible mast of 10.14m length. The motion of the telescope optical axis on the detectors during each observation is measured by a laser metrology system and matches the pre-launch predictions of the thermal flexing of the mast as the spacecraft enters and exits the Earths shadow each orbit. However, an additional motion of the telescope field of view was discovered during observatory commissioning that is associated with the spacecraft attitude control system and an additional flexing of the mast correlated with the Solar aspect angle for the observation. We present the methodology developed to predict where any particular target coordinate will fall on the NuSTAR detectors based on the Solar aspect angle at the scheduled time of an observation. This may be applicable to future observatories that employ optics deployed on extendable masts. The automation of the prediction system has greatly improved observatory operations efficiency and the reliability of observation planning., Comment: 12 pages, 11 figures, in proceedings of SPIE conference 9910

The Nuclear Spectroscopic Telescope Array (NuSTAR) satellite is a NASA Small Explorer mission designed to operate the first focusing high-energy X-ray (3-79 keV) telescope in orbit. Since the launch in June 2012, all the NuSTAR components have been working normally. The focal plane module is equipped with an 155Eu radioactive source to irradiate the CdZnTe pixel detectors for independent calibration separately from optics. The inflight spectral calibration of the CdZnTe detectors is performed with the onboard 155Eu source. The derived detector performance agrees well with ground-measured data. The in-orbit detector background rate is stable and the lowest among past high-energy X-ray instruments.

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (5 - 80 keV) telescope to orbit. NuSTAR will offer a factor 50 - 100 sensitivity improvement compared to previous collimated or coded mask imagers that have operated in this energy band. In addition, NuSTAR provides sub-arcminute imaging with good spectral resolution over a 12-arcminute field of view. After launch, NuSTAR will carry out a two-year primary science mission that focuses on four key programs: studying the evolution of massive black holes through surveys carried out in fields with excellent multiwavelength coverage, understanding the population of compact objects and the nature of the massive black hole in the center of the Milky Way, constraining explosion dynamics and nucleosynthesis in supernovae, and probing the nature of particle acceleration in relativistic jets in active galactic nuclei. A number of additional observations will be included in the primary mission, and a. guest observer program will be proposed for an extended mission to expand the range of scientific targets. The payload consists of two co-aligned depth-graded multilayer coated grazing incidence optics focused onto solid state CdZnTe pixel detectors. To be launched in early 2012 on a Pegasus rocket into a low-inclination Earth orbit. NuSTAR largely avoids SAA passages, and will therefore have low and stable detector backgrounds. The telescope achieves a 10.15-meter focal length through on-orbit deployment of all mast. An aspect and alignment metrology system enable reconstruction of the absolute aspect and variations in the telescope alignment resulting from mast flexure during ground data processing. Data will be publicly available at GSFC's High Energy Astrophysics Science Archive Research Center (HEASARC) following validation at the science operations center located at Caltech.