The Kepler Science Operations Center (SOC) is responsible for the configuration and management of the
SOC Science Processing Pipeline, processing of the science data, distributing data and reports to the Science
Office, exporting processed data for archiving to the Data Management Center at the Space Telescope Science
Institute, and generation and management of the target and aperture definitions. We present an overview of
the SOC procedures and workflows for the data the SOC manages and processes. There are several levels of
reviews, approvals, and processing for the various types of data. We describe the process flow from data
receipt through data processing and export, as well as the procedures in place for accomplishing the tasks. The
tools used to accomplish the goals of Kepler science operations will be presented and discussed as well. These
include command-line tools and graphical user interfaces, as well as commercial products. The tools provide a
wide range of functionality for the SOC including pipeline operation, configuration management, and process
workflow implementation. For a demonstration of the Kepler Science Operations Center's processes,
procedures, and tools, we present the life of a quarter's worth of data, from target and aperture table
generation through archiving the data collected with those tables.
The Kepler mission monitors ~ 165, 000 stellar targets using 42 2200 × 1024 pixel CCDs. Onboard storage
and bandwidth constraints prevent the storage and downlink of all 96 million pixels per 30-minute cadence, so
the Kepler spacecraft downlinks a specified collection of pixels for each target. These pixels are selected by
considering the object brightness, background and the signal-to-noise in each pixel, and maximizing the signal-to-
noise ratio of the target. This paper describes pixel selection, creation of spacecraft apertures that efficiently
capture selected pixels, and aperture assignment to a target. Engineering apertures, short-cadence targets and
custom-specified shapes are discussed.
The Stratospheric Observatory for Infrared Astronomy (SOFIA) will enable unique astronomical observations from visible to millimeter wavelengths. AIRES, a long-slit spectrograph with a mid-infrared slit viewing camera, would enable spectral imaging of gas-phase spectral features between 17 and 210 μm with resolving powers from ~60,000 to 5000. The Cryogenic Grating Spectrometer (CGS: AIRES' predecessor) which was flown on NASA's Kuiper Airborne Observatory (KAO) for 13 years, demonstrated the importance of this wavelength range. A 1997 proposal to develop AIRES was selected as the highest-ranked of 19 U.S. competitors for first-generation SOFIA science instruments. Funding was terminated in 2001 due to budget problems associated with an original under estimate and the advent of full cost accounting in NASA. Here we summarize AIRES' expected performance, its science potential, its status, and lessons learned. Highlighted are three successfully accomplished major technical developments: the world's largest monolithic cryogenic grating, cryogenic multiplexing amplifiers for far-infrared germanium photoconductor detectors, and an optical/mechanical design in a package suitable for installation on SOFIA. We show that AIRES would fill a unique role among other spectroscopic capabilities foreseen for space-borne missions. AIRES' capabilities remain a high but unfilled priority for SOFIA, and for the science community in general.
The 2.5 meter (m) effective diameter telescope on SOFIA - the Stratospheric Observatory for Infrared Astronomy - will operate in an open-port cavity which will be closed below operating altitudes by a cavity-door assembly. When
operating, the telescope will view the sky through an aperture defined by an aperture assembly (AA) with a nearly
rectangular opening extending 112 inches (2.84 m) in elevation (roll) and 129 inches (3.27 m) in cross-elevation. The
aperture will be servo-controlled in roll to track the telescope elevation (EL), and the aircraft heading will be adjusted to
maintain the telescope centered on the aperture in cross-elevation (XEL). An upper rigid door (URD) and lower
flexible door (LFD) move with the aperture to minimize the opening into the cavity containing the telescope. This paper
describes basic parameters of the door system, and estimates possible science impacts of its specification, configuration
and planned operation. Topics included are the geometry, expected aerodynamic disturbances, control system, gear life,
influences of radiative and diffraction effects on science instrument performance, testing, operational considerations,
and development status. As designed, the door system is expected not to limit the performance of science instruments or
observatory operational efficiency, but several potential concerns are considered. These include modulation of stray
and diffracted radiation, reliability, and maintainability.
The SOFIA telescope has a silicon carbide secondary mirror and a six degree-of-freedom secondary mirror mechanism. Each of these high-technology items represents a single-point failure mode, because both are essential for operation of the observatory, and neither has a spare. Reduced-performance, relatively inexpensive “backup” hardware can enable a large fraction of the planned SOFIA science observations, and so can help to assure a highly reliable flight program. Accordingly, we have developed an aluminum secondary mirror and derived design requirements for a backup secondary mirror mechanism that will meet minimum performance needs.
The optical design is presented for a long-slit grating spectrometer known as AIRES (Airborne InfraRed Echelle Spectrometer). The instrument employs two gratings in series: a small order sorter and a large steeply blazed echelle. The optical path includes four pupil and four field stops, including two narrow slits. A detailed diffraction analysis is performed using GLAD by Applied Optics Research to evaluate critical trade-offs between optical throughput, spectral resolution, and system weight and volume. The effects of slit width, slit length, oversizing the second slit relative to the first, on- vs off-axis throughput, and clipping at the pupil stops and other optical elements are discussed.
Testing of a 40 to 125 μm Ge:Sb photoconductor array for AIRES (Airborne Infra-Red Echelle Spectrometer) is described. The prototype array is a 2×24 module which can be close-stacked with other modules to provide larger two-dimensional formats. Collecting cones on a 0.08 inch pitch concentrate incident radiation into integrating cavities containing the detectors. The array is read out by two Raytheon SBRC 190 cryogenic multiplexers that also provide a CTIA (capacitive transimpedance amplifier) unit cell for each detector. We have conducted a series of tests to evaluate the array dark current, responsivity and detective quantum efficiency.
In this paper we describe a potential new Explorer-class space mission, the AstroBiology Explorer (ABE), consisting of a relatively modest dedicated space observatory having a 50 cm aperture primary mirror which is passively cooled to T < 65 K, resides in a low-background orbit (heliocenter orbit at 1 AU, Earth drift-away), and is equipped with a suite of three moderate resolution spectrographs equipped with first-order cross-dispersers and large format (1024 X 1024 pixel) near- and mid-IR detector arrays cooled by a modest amount of cryogen.
We have designed and prototyped an array of Ge:Sb photoconductors for use in AIRES, the Airborne InfraRed Echelle Spectrometer, on SOFIA. The 16 X 24 flight array will operate between 33 micrometers and 120 micrometers . In this paper we discuss the testing of a 3 X 3 prototype array and the resulting design of the flight array.
Access to the cavity containing the SOFIA telescope will be severely limited to maintain mirror cleanliness. This will minimize mirror emissivity and extend the time between mirror cleaning/coating cycles, but precludes full access to the telescope for alignment of science instruments. Since there will be over 20 instrument change-outs per year, they must be efficient and trouble-free if SOFIA is to achieve its anticipated flight rate. A telescope assembly alignment simulator (TAAS) is being designed and built to enable verification of most mechanical, electrical, and optical interfaces between a science instrument and the telescope system. It is anticipated that an instrument will typically spend about a week on this simulator to complete its functional check-out and prepare for integration with the SOFIA telescope. This advance work on the simulator will enable the installation of science instruments onto the observatory in less than four hours. The current TAAS design and prototyping activities are described.
NASA's Stratospheric Observatory for IR Astronomy (SOFIA) will enable unprecedented IR acuity at wavelengths obscured from the ground. To help open this new chapter in the exploration of the IR universe, we are developing the Airborne IR Echelle Spectrometer (AIRES) as a facility science instrument. Full funding was awarded for a four year development in October, 1997. The instrument is scheduled to come on-line with the observatory in the Fall of 2001. It will be used to investigate a broad range of phenomena that occur in the interstellar medium. AIRES will use a 1200 mm long, 76 degree blaze angle echelle to combine high resolution spectroscopy with diffraction-limited imaging in the cross-dispersion direction. Its three 2D detector arrays will prove good sensitivity over a decade in wavelength. An additional array will be used as a slit viewer for (lambda) <EQ 28 micrometers to image source morphology and to verify telescope pointing. Our scientific motivation, preliminary optical design and packaging, focal plane configuration, echelle prototyping, and cryostat layout are described.
The idea of interstellar communication with the aid of lasers and the possibility of manipulating natural lasers to this end make the search for lasing cosmic sources a part of the SETI program. Yet, apart from the very weak lasing in the 10 micrometers CO2 band in the Martian and Venusian atmospheres, only one case of possible natural lasing, in the 4.7 micrometers hydrogen Pf(beta) line from the Becklin-Neugenbauer source in Orion, has been reported but never confirmed. Given hundreds of maser sources detected during the 30 years after their first discover in 1965, the lack of detected natural lasers became a tantalizing puzzle. We undertook a search for high-gain hydrogen lasers in the far-infrared spectrum of MWC349, a peculiar star known as a unique source of mm/submm hydrogen masers. We used the facility cryogenic grating spectrometer onboard the Kuiper Airborne Observatory. An efficient criterion of lasing is elaborated using a set of nonlasing, spontaneous emission lines as a reference. The shortest wavelength line showing an excess of radiation in our search is H10(alpha) at 52 micrometers . We briefly discuss possible reasons for the lack of detectable lasers in the visual and near- infrared domains.