POAM II Overview

POAM II Channel Figure
POAM II Channel Figure

The Polar Ozone and Aerosol Measurement II (POAM II) instrument was developed by the Naval Research Laboratory (NRL) to measure the vertical distribution of atmospheric ozone, water vapor, nitrogen dioxide, aerosol extinction, and temperature. POAM II measures solar extinction in nine narrow band channels, covering the spectral range from approximately 350 to 1060 nm.
(See Channel Table and Channel Figure) Solar extinction by the atmosphere is measured using the solar occultation technique; the sun is observed through the Earth's atmosphere as it rises and sets as viewed from the satellite. (See Occultation illustration)

POAM II was launched aboard the French SPOT-3 satellite on 26 September, 1993 into a Sun synchronous polar orbit. As seen from the satellite, the Sun rises in the north polar region and sets in the south polar region 14.2 times per day. Sunrise measurements are made in a latitude band from 55-71 degrees north while sunsets occur between 63-88 degrees south. (See Latitude figure at right) The POAM II mission was interrupted by the failure of the SPOT-3 satellite in November of 1996.

POAM II Occultation Illustration
POAM II Occultation Illustration

Further details about the POAM II instrument can be found in Glaccum, et al. [1996]. The retrieval process is described by [Lumpe et al., 1997]. Some of the science topics that have
been addressed by the POAM measurements are listed in the
Publication List.

POAM II Latitude Figure
POAM II Latitude Figure
POAM II Science Channels
Channel Center Wavelength
Width (nm) Primary Purpose
1 352.3 4.4 Rayleigh Extinction
2 441.6 2.0 NO2 (off peak)
3 448.1 2.1 NO2 (on peak)
4 601.4 14.3 Ozone
5 761.2 2.2 Oxygen (on peak)
6 781.0 16.7 Oxygen (off peak)
7 921.0 2.1 H2O (off peak)
8 936.4 2.3 H2O (on peak)
9 1060.3 11.1 Aerosol Extinction

POAM III Overview

The Polar Ozone and Aerosol Measurement III (POAM III) instrument is similar to POAM II. POAM III is carried by the SPOT-4 spacecraft sponsored by the Centre National d'Etudes Spatiales (CNES), the French Space Agency. SPOT-4 is the most recent in the SPOT series of remote sensing spacecraft: the acronym "SPOT" stands for "Satellite Pour l'Observation de la Terre". SPOT-4 was launched on an Ariane-4 rocket in March 1998, from CNES' facility in Kourou, French Guayana. The orbit is essentially identical to that of POAM II (see Latitude figure above). POAM III includes several improvements relative to POAM II. It is more sensitive, and will therefore be able to measure deeper into the atmosphere. It has two Sun-sensor quadrant detectors instead of one: a 10 degree Wide Field Sun Sensor as well as the 1 degree Narrow Field Sun Sensor used in POAM II. The Wide Field Sun Sensor will simplify initial acquistion of the Sun at the beginning of sunrise and sunset events. The interference filters used by the science channels in POAM III were manufactured via a newer, better technology than that for the POAM II filters. And finally, the wavelenths and bandwidths of the science channels differ slightly from those in POAM II. The science channels for POAM III are given in the table below (with all wavelengths in nanometers). POAM III, like POAM II, was fabricated by ThermoTrex Corporation in San Diego, California.

POAM III Science Channels
Channel Center Wavelength
Width (nm) Primary Purpose
1 353.4 9.71 Rayleigh Extinction
2 439.6 2.1 NO2 (off peak)
3 442.2 2.1 NO2 (on peak)
4 603 17.7 Ozone
5 761.3 2.3 Oxygen (on peak)
6 779 10.2 Oxygen (off peak)
7 922.4 2.6 H2O (off peak)
8 935.9 2.9 H2O (on peak)
9 1018 11.6 Aerosol Extinction

The POAM III instrument failed on Dec 5, 2005.
For more information on POAM II, contact the Principal Investigator.