The new infrared sensor technology (NIRST) is an infrared radiometer on board the SAC-D/Aquarius mission, launched on June 10, 2011. It is composed of middle wave infrared (MWIR) and a long wave infrared (LWIR) cameras, with three arrays of 512 microbolometers each. The three MWIR camera arrays operate in the [3.4,4.2]-μm spectral range, whereas LWIR camera arrays 1 and 2 operate in the [10.4,11.3]-μm spectral range and array 3, in the [11.4,12.3]-μm spectral range. NIRST also has a pointing Be mirror that covers the range of [30 deg, 60 deg], where 45 deg corresponds to nadir pointing. The aim of this work is to present the on-ground NIRST mirror’s characterization. The characterization was performed in an ambient environment by acquiring data at three different pointing angles, β={30 deg;45 deg;60 deg}, at several blackbody sources’ temperatures for both cameras. The on-ground mirror characterization revealed that the laboratory blackbody sources used present a temperature gradient on their emitting surfaces. The results also reveal the system response to be affected by the pointing angle, i.e., the data at 60 deg was noisier that at 30 deg.
The aim is to present a first approach for the on-ground radiometric characterization of the new infrared sensor technology (NIRST) instrument. NIRST is an infrared radiometer on board the SAC-D/Aquarius mission, launched on June 10, 2011. It is composed of a middle-wave infrared and a long-wave infrared camera, with three arrays of 512 microbolometers each, and has also a pointing Be mirror. In order to perform the on-ground radiometric characterization, several measurements are taken using blackbody sources. Aiming to obtain a set of absolute radiometric coefficients for each pixel of each microbolometer array, relating digital numbers and brightness temperature or its equivalent in radiated power, polynomial fits are performed. Interpixel characterization to obtain relative calibration coefficients is also performed, relating the counts of an arbitrary pixel to those of a reference pixel. The choice of polynomial order for both absolute and relative calibration functions, as well as the election of reference pixels, are analyzed. Finally, a pointing angle characterization is performed. This approach leads to high polynomial orders for both absolute and relative calibrations, indicating that a new approach for NIRST radiometric characterization is required to catch-up the nonlinearity.
The use of uncooled microbolometer detectors for space infrared (IR) imaging application requires high optical
throughput, which leads to very fast optical design (~f/1). This directly translates into stringent requirements for
components, assembly and alignment. The Institut National d'Optique (INO) in Quebec City, Canada, designed such a
system for the NIRST IR Camera. The instrument is part of the Aquarius/SAC-D satellite, a cooperative mission
conducted jointly by NASA and the Comisión Nacional de Actividades Espaciales (CONAE) of Argentina.
Due to the tight volume and mass allocation, the NIRST camera module is an all refractive design. Since the Camera is
made of two lens barrels co-registered to cover the same ground area at different wavelength bands, it also adds coregistration
alignment constraints.
This paper presents the optomechanical solutions and alignment scheme that enabled the successful design and flight
qualification. Trade-off study between thermally induced stress and structural stiffness of the lens RTV bond is
discussed. Special attention is given to lens subcell alignment integrity under random vibration encountered during
launch. Detailed Finite Element Analysis (FEA) is used to check early design assumptions. Test results of the final
vibration campaign are also presented.
Aquarius/SAC-D is a cooperative international mission conducted jointly by the National Aeronautics and Space
Administration of the United States of America and the Comisión Nacional de Actividades Espaciales of Argentina.
Jointly developed by CONAE and the Canadian Space Agency, the New IR Sensor Technology (NIRST) instrument will
monitor high temperature events. NIRST has one band in the mid-wave infrared and two bands in the thermal infrared.
The baseline design of the NIRST is based on microbolometer technology developed jointly by INO and the CSA. This
paper will first present an overview of the design of the NIRST camera module. The manufacturing and qualification
activities for the Flight Model will be described and key performance parameters, as measured during the verification
campaign, will be reported.
Aquarius/SAC-D is a cooperative international mission conducted jointly by the National Aeronautics and Space
Administration (NASA) of the United States of America (USA) and the Comisión Nacional de Actividades Espaciales
(CONAE) of Argentina. The overall mission targets the understanding of the total Earth system and the consequences of
the natural and man-made changes in the environment of the planet. Jointly developed by CONAE and the Canadian
Space Agency (CSA), the New IR Sensor Technology (NIRST) instrument will monitor high temperature events on the
ground related to fires and volcanic events, and will measure their physical parameters. Furthermore, NIRST will take
measurements of sea surface temperatures mainly off the coast of South America as well as other targeted opportunities.
NIRST has one band in the mid-wave infrared centered at 3.8 um with a bandwidth of 0.8 um, and two bands in the
thermal infrared, centered respectively at 10.85 and 11.85 um with a bandwidth of 0.9 um. The temperature range is
from 300 to 600 K with an NEDT < 0.5 K for the mid-infrared band and from 200 to 400 K with an NEDT < 0.4 K for
the thermal bands. The baseline design of the NIRST is based on micro-bolometer technology developed jointly by INO
and the CSA. Two arrays of 512x3 uncooled bolometric sensors will be used to measure brightness temperatures. The
instantaneous field-of-view is 534 microradians corresponding to a ground sampling distance of 350 m at the subsatellite
point. A pointing mirror allows a total swath of +/− 500 km. This paper describes the detailed design of the
NIRST camera module. Key performance parameters are also presented.
NIRST is a pushbroom scanning infrared radiometer that makes use of 512×2 arrays of resistive microbolometers. This instrument comprises mainly two cameras, one operating in the spectral band of 3.4-4.2 μm (band 1) and the other in the bands of 10.4-11.3 (band 2) and 11.4-12.3 μm (band 3). It is intended for the retrievals of forest fire and sea surface temperatures in the Aquarius / SAC-D mission. In this mission the satellite will be launched into a Sun Synchronous polar orbit with an ascending node at 6 PM. This orbit suits the need of discriminating forest fires from solar reflections. NIRST is designed to achieve a spatial resolution of 350 m and a swath width of 180 km at nadir. Its field of view can be steered across track up to 500 km on each side to shorten the revisit time.
To measure fire intensity temperatures NIRST will perform multispectral scans of ground area in bands 1 and 2 and the acquired data will be analyzed using a double band algorithm. The microbolometer detectors have been designed to exhibit useful dynamic range for this application. It is projected that the detector response in band 1 saturates only when NIRST scans a 350 m ground pixel of average temperature of 700 K. The use of the data acquired in bands 2 and 3 allows for the retrieval of sea surface temperature by means of the split algorithm technique.
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