The Wide-Field Infrared Survey Explorer (WISE) is a MIDEX mission that is being developed by the Jet Propulsion Laboratory (JPL) to address several of NASA's Astronomical Search of Origins (ASO) objectives. The WISE instrument, developed by the Space Dynamics Laboratory (SDL), includes a cryogenically cooled telescope (at < 13K) and four focal plane assemblies (2 at 7.6K, 2 at 32K). Cooling of the instrument is accomplished by a dual-stage solid hydrogen cryostat that is developed by the Lockheed Martin Advanced Technology Center (LM-ATC). This paper provides a combined overview of the WISE cryostat design and thermal support system.
We present test data for a solid ZnSe air gapped etalon with free spectral range 3 cm-1 and finesse >70 (i.e., spectral resolution <0.043 cm-1). We present an instrument concept, the Tropopsheric Ozone Sounding (TOS) Dual Etalon Cross Tilt Order Sorting Spectrometer (DECTOSS), that would use an etalon like this to acquire nadir data at resolution <0.06 cm-1 and signal to noise the order 1000 on a range from 1036 to 1071 cm-1 in footprints with crosstrack dimension selectable (e.g., the order tens to hundreds of km), and with along track dimension the order 17 km. Instrument accommodation is the order 25 kg, 110 W and 1 mbps. We present linear error analysis for retrieval of tropospheric ozone from the data acquired by the TOS-DECTOSS. Indication is that more than 2.5 vertical layers of information on tropospheric information are retrievable. An example of the deployment of the TOS-DECTOSS would be as an instrument of opportunity (IOO) add on to the US National Polar-orbiting Operational Environmental Satellite System (NPOESS). The huge advantage of the TOS-DECTOSS as compared with UV techniques for tropospheric ozone measurement is that it the can be used both day and night, the latter is not possible in the UV. The considerable advantage in signal to noise compared with a Fourier Transform Spectrometer (FTS) for tropospheric ozone measurement, on considering that for a given footprint the DECTOSS and FTS integration times are comparable, is that the DECTOSS noise per spectral sample is dominated by statistical fluctuations of signal photons that are passed through its narrow 0.06 cm-1 bandpass, while for a similar FTS spectral sample the noise is due to fluctuations of the signal photons through the FTS bandpass of tens of cm-1. The TOS-DECTOSS signal to noise advantage on the FTS is also enhanced in that the spectral sample density of the TOS-DECTOSS data is more than one hundred times larger than for the FTS.
Multi Layer Insulation (MLI) performance at cold boundary temperatures above 80K to 100K have been well characterized. Further, Lockheed Martin has found that at these temperatures, a blanket’s performance can be well represented by analytic expressions, so long as edge effects, local compressions, and blanket layer density are controlled during the blanket installation. Testing a cold boundary temperatures of 4.2K for the superfluid helium Gravity Probe-B program also found that these same relationships tend to deviate considerably from measurements by a significant margin. Between 4.2K and 80K, no data has been published that quantifies the point where this deviation becomes significant.
This lack of data has the potential for a major impact in the thermal subsystem performance for systems that operate at 30K to 80K cold boundary temperatures. The Next Generation Space Telescope (NGST), Terrestrial Planet Finder (TPF), and Constellation-X are systems that benefit from this data, as they all require passive cooling of critical observatory components to between 30K and 40K. To meet each system’s cooling requirement with low performance risk, large design margins must currently be incorporated in the baseline design.
This paper summarizes testing performed with cold boundary temperatures at liquid nitrogen (77K), solid nitrogen (47K). These measurements fill the gap between 4.2K and 80K and provide MLI design data at low boundary temperatures that are relevant for future NASA initiatives. Commentary is also provided on some limited cold boundary testing with liquid neon (25K) and solid neon (17K).
In this paper we focus on the status and development of critical detector and cooler technology in support of our instrument concept for a Geosynchronous orbiting Nadir Etalon Sounding Spectrometer (GeoNESS) for temperature, moisture and trace species. The concept is a technology derivative of the Cryogenic Limb Array Etalon Spectrometer (CLAES) which is deployed on the NASA Upper Atmospheric Research Satellite (UARS).
The paper describes the Cryogenic Limb Array Etalon Spectrometer (CLAES) launched on September 12, 1991 aboard the NASA Goddard's Upper Atmosphere Research Satellite the purpose of which is to measure the global concentrations of stratospheric species and their temperature, as a function of altitude. Particular attention is given to the design-level thermal predictions and their correlation to the results of ground tests, and to the on-orbit performance of CLAES. Also presented are data on the cryostat's thermal performance during ground operations, at spacecraft integration and during launch preparations. The CLAES functional block diagram and the cryostat schematic diagram are included.
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