The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (6 - 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 eld 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 the 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 scientic targets. The payload consists of two co-aligned depth-graded multilayer coated grazing incidence optics focused onto a 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 passage, and will therefore have low and
stable detector backgrounds. The telescope achieves a 10.14-meter focal length through on-orbit deployment of an extendable mast. An aspect and alignment metrology system enable reconstruction of the absolute aspect and variations in the telescope alignment resulting from mast exure during ground data processing. Data will
be publicly available at GSFC's High Energy Archive Research Center (HEASARC) following validation at the science operations center located at Caltech.
The SIM Lite Astrometric Observatory will be the first space-based Michelson interferometer operating in the visible
wavelength, with the ability to perform ultra-high precision astrometric measurements on distant celestial objects. SIM
Lite data will address in a fundamental way questions such as characterization of Earth-mass planets around nearby
stars. To accomplish these goals it is necessary to rely on a model-based systems engineering approach - much more so
than most other space missions. This paper will describe in further detail the components of this end-to-end performance
model, called "SIM-sim", and show how it has helped the systems engineering process.
This paper examines how narrow-angle (NA) processing of data from the SIM Lite optical interferometry mission can be
undertaken when realistic spacecraft and mission operational constraints are taken into account. Using end-to-end
mission simulations we show that the goal of 1 μas single measurement accuracy (SMA) is obtainable, and hence the
detection of earth-like planets is achievable with the SIM Lite mission.
In this paper we discuss the use of an innovative SIM simulator,
called SIMsim, to perform end-to-end simulations of the SIM mission.
The inputs to the simulator are a physically-based parameterization of
the major SIM error sources and the output is the mission astrometric
accuracy for various observing scenarios such as narrow-angle (NA) and
wide-angle (WA) observations. The primary role of SIMsim is to
validate the SIM astrometric error budget (AEB), but it is also being
used to study a variety of mission performance issues as well as being
a test-bed for prototype data reduction algorithms. SIMsim is giving
us confidence that the SIM AEB is a valid estimate of mission
performance. It also is illustrating where analytical formulas for
estimating certain effects breakdown and a numerical approach has to
We present the basic elements and first results of an end-to-end simulation package whose purpose is to test the validity of the Space Interferometer Mission design. The fundamental simulation time step is one millisecond, with substructure at 1/8 ms, and the total duration of the simulation is five years. The end product of a given 'wide-angle' astrometry run is an estimated grid star catalog over the entire sky with an accuracy of about 4 micro-arcseconds.
SIMsim is divided into five separate modules that communicate via data pipes. The first generates the 'truth' data on the spacecraft structure and laser metrology. The second module generates uncorrupted fringes for the three SIM interferometers, based on the current spacecraft orientation, target stars' positions, etc. The third module reads out the CCD white light fringe data at specified times, corrupting that and the metrology data with appropriate errors. The data stream out of this module represents the basic data stream on the simulated spacecraft. The fourth module performs fringe-fitting tasks on this data, recovering the total path delay, and the fifth and final module inverts the entire metrology/delay dataset to ultimately determine the instantaneous path delay on a fiducial baseline fixed in space. (Pathlength feed forward is used every few milliseconds to re-position the interferometer to keep the fringes in the delay window.) The average of all such delays over an integration time (typically 30 s) is reported as one of several hundred thousand measured stellar delays over the five-year period, which are then inverted to produce the simulated catalog. Future plans include taking into account more sources of error from the SIM error budget and including narrow angle observations in the observing plan.
We will use the astrometric capabilities of the SIM to answer three key questions about active galactic nuclei: 1)Does the separation of the radio core and optical photocenter of quasars change on the same timescale as their photometric variability, or is the separation stable? 2)Does the most compact optical emission from an active galactic nucleus come from an accretion disk or from a relativistic jet? 3)Do the cores of galaxies harbor binary supermassive black holes remaining from galaxy mergers? We will compare the radio and optical positions of quasars used in the tie between optical and radio celestial reference frames. During the first year after launch, we will be able to show whether the frame tie will be limited by 'astrophysical noise'.
The LAser-Stabilized Imaging Interferometer (LASII) concept is being developed as an astronomical telescope for the next generation of optical resolution beyond Hubble Space Telescope (HST). The essential ingredients are: a rigid and stable structure to minimize mechanical and thermal distortion, active control of the optical geometry by a laser metrology system, a self-deploying structure fitting into a single launch vehicle, and ultraviolet operation. We have modified earlier design concepts to fit the scale of an intermediate sized NASA mission. Our present design calls for 24 0.5 m apertures in a Mills Cross configuration, supported on four trusses. A fifth truss perpendicular to the primary surface would support the secondary mirror and the laser metrology control points. Either separate interferometers or two guide telescopes would track guide stars. This instrument would have about 6 times the resolution of HST in the visible and the same collecting area. The resolution would reach 2.5 mas at 150 nm. The primary trusses would fold along the secondary truss for launch, and automatically deploy on orbit. Possible orbits are sun-synchronous at 900 km altitude, high earth orbit or solar orbit. Infrared capability could be included, if desired.