NAST OVERVIEW
The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Aircraft Sounding Testbed (NAST) is comprised of a suite of airborne infrared and microwave spectrometers.
NAST is being developed for the Integrated Programs Office (IPO) as part of a risk reduction effort for future instruments proposed to fly on the future NPOESS satellites and in turn it will provide the scientific community with valuable measurements of the atmosphere and surface from a high altitude platform.
The objectives of NAST are to provide airborne infrared and microwave spectral radiances during field experiments sufficient to:
- Define optimal spectral characteristics of IR and MW sounders for the NPOESS;
- Define spatial resolution and scan geometry characteristics of NPOESS sounders required to optimize soundings in the presence of clouds;
- Validate parameter retrieval algorithms and expected retrieval accuracies for different climatic zones, meteorological and surface conditions, and cloud situations;
- Demonstrate the utility of the NPOESS specified sounding system for observing significant atmospheric processes (e.g., storm genesis and evolution, jet stream position and intensity, sea breeze phenomena, fog formation and dissipation, clear air turbulence, precipitation and cloudiness, etc.);
- Demonstrate the utility of NAST sounding products in regional mesoscale Numerical Weather Prediction (NWP) models to validate expected improvements in NWP using high vertical resolution satellite sounding data; and
- Investigate the utility of NAST data for the retrieval of other NPOESS EDR's (e.g., sea and land surface temperature and emissivity, geometrical and optical properties of clouds, soil moisture, ice content, greenhouse and pollutant gas concentration and profiles, etc.).
NASA ER-2 high altitude research platform at Patrick AFB, FL during CAMEX-3
activities.
Both NAST-I and NAST-MTS (microwave spectrometer) are housed in the superpod.
NAST-I resides in the forward compartment of the superpod while NAST-MTS resides
in the aft compartment.
NAST-I
The NAST-I is a high resolution Michelson interferometer, developed at MIT Lincoln Laboratory, that derives its heritage from the non-scanning High resolution Interferometer Sounder (HIS) developed by researchers at the University of Wisconsin Space Science and Engineering Center (UW-SSEC).The infrared radiance measurements obtained from the NAST-I instrument provide detailed spectral characteristics of the atmosphere and land surface which yield detailed atmospheric temperature and water vapor profiles derived from either physical or regression based retrieval algorithms.
NAST-I Flight Instrument Specifications |
|
| Spectral Resolution | 0.25 cm-1 |
| Spectral Response: LW | 645 - 1300 cm -1 |
| Spectral Response: MW | 1290 - 2000 cm-1 |
| Spectral Response: SW | 1980 - 2700 cm-1 |
| Spatial Resolution | 2.6 km @ 20 km |
| Scan Width | +/- 48o |
| Number of Elements/Scan Line | 13 earth spots |
| NEDT | < 0.1 - 0.25 K @ 260 K |
| Size | Fits Super Pod |
| Weight | 127 kg |
| Power | 970 W |
| ER-2 Flight Location | Super Pod |
 |
<- NAST-I Interferometer in the
right forward compartment |
 |
NAST-M
The NAST-M is a scanning microwave radiometer, which has a nadir ground resolution of ~2.5 km and scans from -58 to +78 degrees from nadir.
Spectral Bands |
Channels |
Range (GHz) |
DTrmsK |
DTrms(5-km) |
WF Altitude (mm H2O) |
Oxygen Band |
8 |
50.3 - 56.02 |
0.19 - 0.23 |
0.07 - 0.08 |
Surface to 100 mb |
Oxygen Line |
7 |
118.75 +- 0.45 - 3.5 |
0.19 - 0.61 |
0.07 - 0.22 |
Surface (50 mm) to 80 mb |
Water Line |
7 |
166, 183.3 +- 1 - 10 |
0.25 - 0.6 |
0.09 - 0.22 |
(30 - 0.5) |
Oxygen Line |
7 |
424.76 +- 0.28 - 3.25 |
0.34 - 1.0 |
0.12 - 0.35 |
600 mb (3 mm) to 60 mb |
NAST-M data products include
- Post Flight: preliminary brightness temperature images (all frequencies), precipitation index +-30o, ~2.5 km resolution, available via internet ftp.
- Post Mission: temperature and relative humidity profile images (~2.5 km resolution) available via internet ftp.
- Research Products: cloud characterization--rain rate, particle size, and cloud top altitude.
