Gordon Tajiri

The Nuclear Spectroscopic Telescope Array (NuSTAR): optics overview and current status

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission scheduled for launch in February 2012. NuSTAR will deploy two imaging CdZnTe spectrometers in the 6-79 keV energy band. The two NuSTAR optics utilize multilayer-coated, thermally-slumped glass integrated into a titanium-glass-epoxy-graphite composite structure, along with an extendable mast, to obtain 10.15 meter focal length. Using this approach, the NuSTAR optics will obtain subarcminute imaging with large effective area over its entire energy band. NuSTARs conic-approximation Wolter-I optics are the first true hard X-ray focusing optics to be deployed on a satellite experiment. We report on the design of the NuSTAR optics, present the status of the two flight optics under construction, and report preliminary measurements that can be used to predict performance.

Fabrication of the NuSTAR flight optics

We describe the fabrication of the two NuSTAR flight optics modules. The NuSTAR optics modules are glass-graphiteepoxy composite structures to be employed for the first time in space-based X-ray optics by NuSTAR, a NASA Small Explorer schedule for launch in February 2012. We discuss the optics manufacturing process, the qualification and environmental testing performed, and briefly discuss the results of X-ray performance testing of the two modules. The integration and alignment of the completed flight optics modules into the NuSTAR instrument is described as are the optics module thermal shields.

NuSTAR hard x-ray optics design and performance

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA satellite mission scheduled for launch in 2011. Using focusing optics with multilayer coating for enhanced reflectivity of hard X-rays (6-79 keV), NuSTAR will provide a combination of clarity, sensitivity and spectral resolution surpassing the largest observatories in this band by orders of magnitude. This advance will allow NuSTAR to test theories of how heavy elements are born, discover collapsed stars and black holes on all scales and explore the most extreme physical environments. We will present an overview of the NuSTAR optics design and production process and detail the optics performance.

NuSTAR hard x-ray optics

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a small explorer (SMEX) mission currently under an extended Phase A study by NASA. NuSTAR will be the first satellite mission to employ focusing optics in the hard X-ray band (8-80 keV). Its design eliminates high detector backgrounds, allows true imaging, and permits the use of compact high performance detectors. The result: a combination of clarity, sensitivity, and spectral resolution surpassing the largest observatories that have operated in this band by orders of magnitude. We present an overview of the NuSTAR optics design and production process. We also describe the progress of several components of our independent optics development program that are beginning to reach maturity and could possibly be incorporated into the NuSTAR production scheme. We then present environmental test results that are being conducted in preparation of full space qualification of the NuSTAR optics.

The FIREBall fiber-fed UV spectrograph

FIREBall (Faint Intergalactic Redshifted Emission Balloon) had a successful first engineering flight in July of 2007 from Palestine, Texas. Here we detail the design and construction of the spectrograph. FIREBall consists of a 1m telescope coupled to a fiber-fed ultraviolet spectrograph flown on a short duration balloon. The spectrograph is designed to map hydrogen and metal line emission from the intergalactic medium at several redshifts below z=1, exploiting a small window in atmospheric oxygen absorption at balloon altitudes. The instrument is a wide-field IFU fed by almost 400 fibers. The Offner mount spectrograph is designed to be sensitive in the 195-215nm window accessible at our altitudes of 35-40km. We are able to observe Lyα, as well as OVI and CIV doublets, from 0.3 < z < 0.9. Observations of UV bright B stars and background measurements allow characterization of throughput for the entire system and will inform future flights.

The Rainwater Memorial Calibration Facility for X-Ray Optics

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. The ground calibration of the optics posed a challenge as the need to suppress finite source distance effects over the full optic and the energy range of interest were unique requirements not met by any existing facility. In this paper we present the requirements for the NuSTAR optics ground calibration, and how the Rainwater Memorial Calibration Facility, RaMCaF, is designed to meet the calibration requirements. The nearly 175 m long beamline sports a 48 cm diameter 5–100 keV X-ray beam and is capable of carrying out detailed studies of large diameter optic elements, such as the NuSTAR optics, as well as flat multilayer-coated Silicon wafers.

Evaluation of epoxy for use on NuSTAR optics

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer (SMEX) mission which employs two focusing optics. The optics are composed of stacks of thin mirror shells and spacers. Epoxy is used to bond the mirror shells to the spacers and is a crucial component in determining the structural and optical performance of the telescopes. We describe the epoxy selection for NuSTAR optics, emphasizing those epoxy characteristics essential to obtaining good optical performance.

Progres on large-scale, low-cost Si(Li) detector fabrication for the GAPS balloon mission

The General Antiparticle Spectrometer (GAPS) experiment is an indirect dark matter search that aims to detect low-energy antideuterons resulting from dark matter annihilations and decays in the Galactic halo. Layers of semiconducting lithium-drifted silicon (Si(Li)) tracking detectors are essential to the success of the GAPS detection and background rejection scheme, requiring ~22.5 square meters of Si(Li) active area with a channel energy resolution of ~3 keV. To produce this large volume of detectors, we are pursuing a process that can provide the required performance and high yield at approximately two orders of magnitude less cost per unit area than commercially acquired detectors.