Engineering topics
Aumann, Hartmut
Publications and source records attributed to Aumann, Hartmut.
The CubeSat Infrared Atmospheric Sounder (CIRAS), Pathfinder for the Earth Observing Nanosatellite-Infrared (EON-IR)
The CubeSat Infrared Atmospheric Sounder (CIRAS) will measure upwelling infrared radiation of the Earth in the MWIR region of the spectrum from space on a CubeSat. CIRAS will demonstrate two new infrared sounding technologies. The first is a 2D array of High Operating Temperature Barrier Infrared Detector (HOT-BIRD) material, selected for its high uniformity, low cost, low noise and higher operating temperatures than traditional materials. The detectors are hybridized to a commercial ROIC and commercial camera electronics. The second technology is an MWIR Grating Spectrometer (MGS) to be designed and developed by Ball Aerospace to provide imaging spectroscopy for atmospheric sounding in a CubeSat volume. The MGS has no moving parts and is based on heritage spectrometers including the Ball Aerospace Spaceborne Infrared Atmospheric Sounder for GEO (SIRAS-G) IIP of 2007. JPL will develop the mechanical, electronic and thermal subsystems for CIRAS. The spacecraft will be a commercially available CubeSat. The integrated system will be a complete 6U CubeSat capable of measuring temperature and water vapor profiles with good lower tropospheric sensitivity. The CIRAS is the first step towards the development of an Earth Observing Nanosatellite Infrared (EON-IR) for potential use in a future operational forecasting system.
Cross Calibration and Validation Using CLARREO
The presentation focuses on study questions, effort, and result. Study questions include a focus on MW/LW, error sources and what can be expected, how validation will be performed and what resolution is required, and spatial resolution required for cross-calibration. Study effort includes empirical approach by examining AIRS ,IASI and MODIS cross-calibration methods already in place and estimate the number of clear and Dome C observations possible versus spatial resolution. Study results include 5000 sampler per cross-calibration recommended, insufficient cloud free and Dome C AWS observations for cross calibration and validation at 100km, and less than 20 km IFOV at 100 km swath needed to achieve sufficient samples for cross-calibration of CLARREO.
AIRS Science Accomplishments Version 4.0/Plans for Version 5
This talk is about accomplishments with AIRS data and what we have learned from almost three years of data what part of this is emerging in Version 4.0 what part we would like to see filtering into Version 5.0 and what part constitute limitations in the AIRS requirements, such as spectral and spatial resolution, which have to be deferred to the wish list for the next generation hyperspectral sounder. The AIRS calibration accuracy at the 1OOmK and stability at the 6 mK/year level are amazing. It establishes the unique capability of a cooled grating array spectrometer in Earth orbit for climate research. Data which are sufficiently clear to match the radiometric accuracy of the instrument, have a yield of less than 1%. This is OK for calibration. The 2616/cm window channel combined with the RTG.SST for tropical ocean allow excellent assessment radiometric calibration accuracy and stability. For absolute calibration verification 100mK is the limit due to cloud contamination. The 10 micron window channels can be used for stability assessment, but accuracy is limited at 300mK due to water continuum absorption uncertainties.
The Precision and Accuracy of AIRS Level 1B Radiances for Climate Studies
We investigate uncertainties in the Atmospheric Infrared Sounder (AIRS) radiances based on in-flight and preflight calibration algorithms and observations. The global coverage and spectra1 resolution ((lamda)/(Delta)(lamda) ~ 1200) of AIRS enable it to produce a data set that can be used as a climate data record over the lifetime of the instrument. Therefore, we examine the effects of the uncertainties in the calibration and the detector stability on future climate studies. The uncertainties of the parameters that go into the AIRS radiometric calibration are propagated to estimate the accuracy of the radiances and any climate data record created from AIRS measurements. The calculated radiance uncertainties are consistent with observations. Algorithm enhancements may be able to reduce the radiance uncertainties by as much as 7%. We find that the orbital variation of the gain contributes a brightness temperature bias of < 0.01 K.
The Atmospheric Infrared Sounder- An Overview
The Atmospheric Infrared Sounder (AIRS) was launched in May 2002. Along with two companion microwave sensors, it forms the AIRS Sounding Suite. This system is the most advanced atmospheric sounding system to date, with measurement accuracies far surpassing those available on current weather satellites. The data products are calibrated radiances from all three sensors and a number of derived geophysical parameters, including vertical temperature and humidity profiles, surface temperature, cloud fraction, cIoud top pressure, and profiles of ozone. These products are generated under cloudy as well as clear conditions. An ongoing calibration validation effort has confirmed that the system is very accurate and stable, and many of the geophysical parameters have been validated. AIRS is in some cases more accurate than any other source and can therefore be difficult to validate, but this offers interesting new research opportunities. The applications for the AIRS products range from numerical weather prediction to atmospheric research - where the AIRS water vapor products near the surface and in the mid to upper troposphere will make it possible to characterize and model phenomena that are key for short-term atmospheric processes, such as weather patterns, to long-term processes, such as interannual cycles (e.g., El Nino) and climate change.
Initial Processing of Infrared Spectral Data
The Atmospheric Infrared Spectrometer (AIRS) Science Processing System is a collection of computer programs, denoted product generation executives (PGEs), for processing the readings of the AIRS suite of infrared and microwave instruments orbiting the Earth aboard NASA's Aqua spacecraft. Following from level 0 (representing raw AIRS data), the PGEs and their data products are denoted by alphanumeric labels (1A, 1B, and 2) that signify the successive stages of processing. Once level-0 data have been received, the level-1A PGEs begin processing, performing such basic housekeeping tasks as ensuring that all the Level-0 data are present and ordering the data according to observation times. The level-1A PGEs then perform geolocation-refinement calculations and conversions of raw data numbers to engineering units. Finally, the level-1A data are grouped into packages, denoted granules, each of which contain the data from a six-minute observation period. The granules are forwarded, along with calibration data, to the Level-1B PGEs for processing into calibrated, geolocated radiance products. The Level-2 PGEs, which are not yet operational, are intended to process the level-1B data into temperature and humidity profiles, and other geophysical properties.