NASA DC-8

Airborne Sensors


Part of the CIMSS Web

MODIS Airborne Simulator

Introduction
CIMSS has developed and flown a variety of airborne earth-observing sensors since 1985. The data acquired by these sensors is used to develop, test, and validate processing algorithms which can eventually be used for spaceborne sensors. For example, a cloud detection algorithm can be developed using data acquired by an airborne imager and tested over a variety of earth scenes while a similar spaceborne sensor is still under development. When the spaceborne sensor is launched, the processing algorithm can be applied to the data with confidence because it has already been proven with airborne data.

Aircraft Platforms
Airborne sensors fly on a variety of different platforms, each with its own unique advantages. High altitude (> 20 km) aircraft provide the widest perspective view of the earth scene below, and can closely simulate the behavior of spaceborne sensors by virtue of being above most of the atmosphere. These platforms typically are flown by a single pilot because of the challenges of life support at high altitude. Medium altitude (> 10 km) aircraft provide a shirt-sleeve environment where scientists can ride along with their sensors to monitor their performance in real-time. Unpiloted aircraft provide the opportunity for longer flights at medium to high altitudes.

Aircraft Platforms used by CIMSS include:

  • ER-2:A high-altitude platform with a flight crew of 1 pilot (photos),
  • DC-8:A medium-altitude platform with a flight crew of 4, and a science crew of up to 18 (photos),
  • Proteus:A high altitude piloted (1 pilot) or unpiloted platform (photos).
Passive Sensors
Passive airborne sensors measure electromagnetic radiation which is either reflected from (solar energy) or emitted by (thermal energy) the earth scene below the aircraft. Sensor types include imagers which collect tens of bands of spectral information at high spatial resolution, and sounders which collect thousands of bands of spectral information at low to moderate spatial resolution.

Passive Imagers used by CIMSS include:

  • MAS: A scanning spectrometer with 50 spectral bands (ER-2),
  • MASTER: A scanning spectrometer very similar to MAS (ER-2 or DC-8),
  • MAMS: A scanning radiometer with 11 spectral bands (ER-2).
Passive Sounders used by CIMSS include:
  • HIS: A nadir viewing interferometer with > 2000 spectral channels (ER-2),
  • Scanning-HIS: A scanning interferometer with > 2000 spectral channels (ER-2 or DC-8),
  • NAST-I: A scanning interferometer with > 2000 spectral channels (ER-2).
Active Sensors
Active airborne sensors send pulses of electromagnetic energy (e.g., a laser beam) towards the earth scene below the aircraft, and then measure the energy which is scattered back towards the sensor (the same principle as radar).

Active Sensors used by CIMSS include:

  • CLS: A nadir pointing laser radar, also known as lidar (ER-2).
 
Updated 7 October 2000
cimssmaster@ssec.wisc.edu		Space Science and Engineering Center
University of Wisconsin-Madison