The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment is one of four experiments that will fly on the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) mission to be launched in May, 2000. The primary science goal of SABER is to achieve major advances in understanding the structure, energetics, chemistry, and dynamics, in the atmospheric region extending from 60 km to 1 80 km altitude. This will be accomplished using the space flight proven experiment approach of spectral broadband limb emission radiometry. SABER will scan the horizon in 10 selected bands ranging from 1.27 im to 17 tm wavelength. The observed vertical horizon emission profiles will be processed on the ground to provide vertical profiles with 2 km altitude resolution, of temperature, 03, H20, and CO2 volume emission rates due to O2(1i), OH(u=3,4,5), OH(i=7,8,9), and NO; key atmospheric cooling rates, solar heating rates, chemical heating rates, airglow losses; geostrophic winds, atomic oxygen and atomic hydrogen. Measurements will be made both night and day over the latitude range from the southern to northern polar regions. The SABER instrument uses an on-axis Cassegrain design with a clam shell reimager. Preliminary test and calibration results show excellent radiometric performance.

For the most part, satellite observations of climate are not presently sufficiently accurate to establish a climate record that is indisputable and hence capable of determining whether and at what rate the climate is changing. Furthermore, they are insufficient for establishing a baseline for testing long‐term trend predictions of climate models. Satellite observations do provide a clear picture of the relatively large signals associated with interannual climate variations such as El Niño‐Southern Oscillation (ENSO), and they have also been used to diagnose gross inadequacies of climate models, such as their cloud generation schemes. However, satellite contributions to measuring long‐term change have been limited and, at times, controversial, as in the case of differing atmospheric temperature trends derived from the U.S. National Oceanic and Atmospheric Administration's (NOAA) microwave radiometers.

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Melting/freezing curves are studied for the single-component Ga and bimetallic eutectic alloys Ga–In, Ga–Sn, Ga–Zn and Ga–Al in small-size cells. These phase-transition studies were conducted at VNIIOFI and SDL in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous platforms. Our prime objective is to develop technology to improve the long-term performance of in-flight blackbody calibration sources of space-borne radiometers. The repeatability of the melting temperature of Ga and the eutectic melting temperatures of Ga–In, Ga–Sn and Ga–Zn fixed points were studied. Our results show that small cells containing Ga and some Ga-based eutectic alloys can be used as melting fixed-point standards.

The SABER instrument on the National Aeronautics and Space Administration Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics satellite continues to provide a long‐term record of Earth's stratosphere, mesosphere, and lower thermosphere. The SABER data are being used to examine long‐term changes and trends in temperature, water vapor, and carbon dioxide. A tacit, central assumption of these analyses is that the SABER instrument radiometric calibration is not changing with time; that is, the instrument is stable. SABER stratospheric temperatures and those derived from Global Positioning System Radio Occultation measurements are compared to examine SABER's stability. Global Positioning System Radio Occultation measurements are inherently stable due to the accuracy and traceability of the measured phase delay rate to the Système Internationale definition of the second. Differences in global annual mean SABER and COSMIC lower stratospheric temperatures show little significant change with time in the 11 years spanning 2007–2017. From this analysis we infer that SABER temperatures are stable to better than 0.1 to 0.2 K per decade.

This paper describes the design of a 10-channel infrared (1 .27 to 16.9 jim) radiometer instrument known as SABER (sounding of the atmosphere usingbroadband emissionradiometry) that will measure earth-limb emissions from the TiMED (thermosphere-ionospheremesosphere energetics and dynamics) satellite. The instrument telescope, designed to reject stray. light from the earth and the atmosphere, is an on-axis Cassegrain design with a clam shell reimager and a one-axis scan mirror. The telescope is cooled below 210 K by a dedicated radiator. The focal plane assembly (consisting of a filter array, a detector array, a Lyot stop and a window) is cooled to 75 Kby a miniature cryogenic refrigerator. The conductive heat load on the refrigerator is minimized by a Keviar support system that thermally isolates the focal plane assembly from the telescope. Kevlar is also used to thermally isolate the telescope from the spacecraft. Instrument responsivity drifts due to changes in telescope and focal plane temperatures as well as other causes are neutralized by an in-flight calibration system. The detectOr airay consists ofdiscrete IJgCdTe, JnSb and InGaAS detectors. Two InGaAS detectors are a new long wavelength type, made by EG&G, that have a long wavelength cutoffof2.33 im at 77 K.1. IPTRODUCTION SABER (sounding ofthe atmosphere using broadband emissionradiomelry) is an earth-limb-scanning radiometer that has been selected as one of the four payload instruments on TIMED (thermosphere-ionosphere-mesosphere energetics and dynamics) satellite to be launched in OctOber 1998. The TIMED orbit altitude is 600 km and the orbit inclination is 74.4 degrees. SABER will look 90 degrees to the ram. The mission life is 2 years.The SABER systems requirement review(SRR) and the conceptual design review (CoDR) were held in April 1 995, and the preliminaiy design review is scheduled for April 1996. Significant modifications to the SABER design described in the literature3 have been made in the last year. Many ofthese modifications resulted because the previous optical design required filters that were impractically thick to correct for chromatic focal shifts across the very wide spectral band covered by SABER. A new optical design that solved this problem and resulted in a much more rugged instrument was developed and is described in this paper. The stray light performance of this new design is excellent. This paper is intended to provide a comprehensive overview ofthe new SABER design. SYSTEM DESIGN -A functional diagram ofthe SABER instrument is shown in Figure 1. A high off-axis rejection telescope collects wanted light and discriminates against unwanted light. The scan mirror scans the instrument field ofview vertically across the earth limb. In orbit the telescope is oriented so the nadir_zenith line is vertical in Figure 1 and local depression angles are measured relative to the horizontal. The baffle opening allows the center of SABER's 1 .4 degree wide field ofview to be scanned across depression angles from 11.148 to 26.168 degrees. Thi...

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A necessary condition for accumulating fundamental climate data records is the use of observation instruments whose stability and accuracy are sufficiently high for climate monitoring purposes; the number of instruments and their distribution in space should be sufficient for measurements with no spatial or temporal gaps. The continuous acquirement of data over time intervals of several decades can only be possible under the condition of simultaneous application of instruments produced by different manufacturers and installed on different platforms belonging to one or several countries.The design of standard sources for pre-flight calibrations and in-flight monitoring of instruments has to meet the most stringent requirements for the accuracy of absolute radiometric measurements and stability of all instruments. This means that the radiometric scales should be stable, accurate, and uniform.Current technologies cannot ensure the high requirements for stability and compatibility of radiometric scales: 0.1% per decade within the 0.3 -3 µm band and 0.01 K per decade within the 3 -25 µm band.It is suggested that this task can be aided through the use of the pure metals or eutectic alloy phase transition phenomenon that always occur at the same temperature. Such devices can be used for pre-flight calibrations and for on-board monitoring of the stability of radiometric instruments. Results of previous studies of blackbody models that incorporate phase transition phenomenon are quite promising. A study of the phase transition of some materials in small cells was conducted for future application in onboard monitoring devices and its results are positive and allow us to begin preparations for similar experiments in space.