The Ultraviolet Explorer (UVEX) mission is built on three scientific pillars: (I) Exploring the low-mass, low-metallicity galaxy frontier; (II) Providing new views of the dynamic universe, and (III) Leaving a broad legacy of modern, deep synoptic surveys. The deep, synoptic all-sky survey includes the Galactic Plane and Magellanic Clouds and achieves depths and resolution matching modern optical/IR surveys with Rubin, Roman, and Euclid. UVEX will follow up the aftermath of GW-detected NS mergers and provide the first rapid UV spectroscopic follow-up of transients. The UVEX payload consists of a single instrument with simultaneous FUV and NUV imaging over a wide (12 deg2) FOV and sensitive R>1000 spectroscopy over a broad band from 1150 – 2650 Å. Placed in a highly elliptical, TESS-like orbit, UVEX achieves low background and high observing efficiency. Frequent ground contacts and rapid slew capability enable UVEX to promptly follow up targets of opportunity, providing the first rapid, deep UV imaging and spectroscopic follow-up capability.
We present here the updated calibration of the Nuclear Spectroscopic Telescope Array, which was performed using data on the Crab accumulated over the last nine years in orbit. The basis for this new calibration contains over 250 ks of focused Crab observations (imaged through the optics) and over 500 ks of stray-light (SL) Crab observations (not imaged through optics). We measured an epoch averaged spectrum of the SL Crab data and define a canonical Crab spectrum of Γ = 2.103 ± 0.001 and N = 9.69 ± 0.02 keV − 1 cm − 2 s − 1 at 1 keV, which we use as our calibration standard. This calibration released in the Calibration Data Base update 20211020 provides significant updates to: (1) the detector absorption component, (2) the detector response function, and (3) the effective area vignetting function. The calibration improves agreement between FPMA and FPMB across detectors with a standard deviation of 1.7% for repeat observations between off-axis angles of 1′ to 4′. As a consequence of the measured SL observations, the absolute flux of the instrument has increased by 5% to 15%, with 5% below 1′ off-axis angle, 10% between 1 and 2′, and 15% above 4′.
We describe a method by which the metrology system of the Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray space observatory, which uses two lasers to characterize the relative motion of the optics and focal plane benches, can be approximated should one laser fail. The two benches are separated by a 10-m-long rigid mast that undergoes small amounts of thermal flexing that needs to be compensated for to produce a nonblurred image. We analyze the trends of mast motion by archival observation parameters to discover whether the mast motion in future observations can be predicted. We find that, using the solar aspect angle, observation date, and orbital phase, we can simulate the motion of one laser by translating the track produced by the other and applying modifications to the resulting mast aspect solution, allowing for the reconstruction of a minimally distorted point spread function in most cases. We will implement the generation of simulated mast files along with the usual NuSTAR data reduction pipeline for contingency purposes. This work has implications for reducing the risk of implementing laser metrology systems on future missions that use deployable masts to achieve the long focal lengths required in high-energy astronomy by mitigating the impact of a metrology laser failure in the extended phase of a mission.
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.
The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy (3-79 keV) X-ray observatory. The NuSTAR project is led by Caltech, which hosts the Science Operations Center (SOC), with mission operations managed by UCB Space Sciences Laboratory. We present an overview of NuSTAR science operations and describe the on-orbit performance of the observatory. The SOC is enhancing science operations to serve the community with a guest observing program beginning in 2015. We present some of the challenges and approaches taken by the SOC to operating a full service space observatory that maximizes the scientific return from the mission.
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) mission was launched on 2012 June 13 and is the first focusing high-energy X-ray telescope in orbit operating above ~10 keV. NuSTAR flies two co-aligned Wolter-I conical approximation X-ray optics, coated with Pt/C and W/Si multilayers, and combined with a focal length of 10.14 meters this enables operation from 3-79 keV. The optics focus onto two focal plane arrays, each consisting of 4 CdZnTe pixel detectors, for a field of view of 12.5 arcminutes. The inherently low background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than 100-fold improvement in sensitivity, and with an effective point spread function FWHM of 18 arcseconds (HPD ~1), NuSTAR provides a leap of improvement in resolution over the collimated or coded mask instruments that have operated in this bandpass. We present in-orbit performance details of the observatory and highlight important science results from the first two years of the mission.
KEYWORDS: Space operations, Sensors, Stars, System on a chip, Ultraviolet radiation, Spectroscopy, Galactic astronomy, Space telescopes, Imaging spectroscopy, Observatories
The Galaxy Evolution Explorer, a NASA small explorer mission, is
performing the first all-sky, deep imaging and spectroscopic surveys
in the space ultraviolet. The prime goal of GALEX is to study star
formation in galaxies and its evolution with time. Now in its fourth year of operations the emphasis of the mission is changing from
completing the primary science goals set at launch to servicing the astronomical community with a guest investigator program that uses 50%
or more of the available observing time. We outline here mission
operations, describe some of the challenges the GALEX team has surmounted,
and some of the changes needed to accomplish the goals of the extended mission.
We describe the Galaxy Evolution Explorer (GALEX) satellite that was launched in April 2003 specifically to accomplish far ultraviolet (FUV) and near ultraviolet (NUV) imaging and spectroscopic sky-surveys. GALEX is currently providing new and significant information on how galaxies form and evolve over a period that encompasses 80% of the history of the Universe. This is being accomplished by the precise measurement of the UV brightness of galaxies which is a direct measurement of their rate of star formation. We briefly describe the design of the GALEX mission followed by an overview of the instrumentation that comprises the science payload. We then focus on a description of the development of the UV sealed tube micro-channel plate detectors and provide data that describe their on-orbit performance. Finally, we provide a short overview of some of the science highlights obtained with GALEX.
We describe the performance results for the Galaxy Evolution Explorer (GALEX) far ultraviolet (FUV) and near ultraviolet (NUV) detectors. The detectors were delivered to JPL/Caltech starting in the fall of 2000 and have undergone approximately 1000 hours of pre-flight system-level testing to date. The GALEX detectors are sealed tube micro-channel plate (MCP) delay line readout detectors. They have a 65 mm diameter active area, which will be the largest format on orbit. The FUV detector has a spectral bandpass from 115 - 180 nm and the NUV detector has a bandpass from 165 - 300 nm. We report here on the performance of the detectors before and after integration into the instrument. Characteristics measured include the background count rate and distribution, gain vs. applied high voltage, spatial resolution and linearity, flat fields, and quantum efficiency.
Christopher Martin, Thomas Barlow, William Barnhart, Luciana Bianchi, Brian Blakkolb, Dominique Bruno, Joseph Bushman, Yong-Ik Byun, Michael Chiville, Timothy Conrow, Brian Cooke, Jose Donas, James Fanson, Karl Forster, Peter Friedman, Robert Grange, David Griffiths, Timothy Heckman, James Lee, Patrick Jelinsky, Sug-Whan Kim, Siu-Chun Lee, Young-Wook Lee, Dankai Liu, Barry Madore, Roger Malina, Alan Mazer, Ryan McLean, Bruno Milliard, William Mitchell, Marco Morais, Patrick Morrissey, Susan Neff, Frederic Raison, David Randall, Michael Rich, David Schiminovich, Wes Schmitigal, Amit Sen, Oswald Siegmund, Todd Small, Joseph Stock, Frank Surber, Alexander Szalay, Arthur Vaughan, Timothy Weigand, Barry Welsh, Patrick Wu, Ted Wyder, C. Kevin Xu, Jennifer Zsoldas
The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750Å and 1750-2800Å) will range from an all-sky survey (limit mAB~20-21) to an ultra-deep survey of 4 square degrees (limit mAB~26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (mAB~20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800Å band. The instrument includes a 50 cm modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey.
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