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Local Weather
Oberpfaffenhofen

The Polar Ozone and Aerosol Measurement (POAM II & III) instruments were developed by the US Naval Research Laboratory to measure atmospheric profiles of ozone, water vapor, nitrogen dioxide, aerosol extinction, using the technique of solar occultation. POAM II was launched on the SPOT-3 satellite in September 1993 and operated until SPOT-3 failed in November 1996. The successor instrument, POAM III, was launched on the SPOT 4 satellite in March 1998, and operated until the instrument failed in December 2005.

Objectives

From the fundamental transmission measurements it is possible to retrieve density profiles of O3, NO2, and H2O, as well as wavelength-dependent aerosol extinction. Under cloud-free conditions POAM III routinely measures well into the troposphere.

Instrument

The POAM II and III instruments are both 9-channel photometers that measure atmospheric extinction at selected bands between 0.35 to 1.07 microns (see tables below). From these bands it is possible to retrieve density profiles of ozone, nitrogen dioxide, and water vapor, as well as wavelength-dependent aerosol extinction. POAM III includes several improvements relative to POAM II. It is more sensitive and is able to measure to lower altitudes than POAM II. Both instruments are in identical orbits, performing 14 measurements per day in each hemisphere on a slowly varying latitude circle. The measurements are confined to the latitude range of 55N-71N in the northern hemisphere, and 63S-88S in the southern hemisphere.

POAM II Science Channels

Channel Center Wavelength (nm) Width (nm) Primary Purpose
1352.34.4Rayleigh Extinction
2441.62.0NO2 (off peak)
3448.12.1NO2 (on peak)
4601.414.3Ozone
5761.22.2Oxygen (on peak)
6781.016.7Oxygen (off peak)
7921.02.1H2O (off peak)
8936.42.3H2O (on peak)
9 1060.3 11.1 Aerosol Extinction

POAM III Science Channels

Channel Center Wavelength (nm) Width (nm) Primary Purpose
1353.49.71Rayleigh Extinction
2439.62.1NO2 (on peak)
3442.22.1NO2 (off peak)
460317.7Ozone
5761.32.3Oxygen (on peak)
677910.2Oxygen (off peak), Aerosol
7922.42.6H2O (off peak)
8935.92.9H2O (on peak)
9101811.6Aerosol Extinction

 

Data Access

General Data Product Level Definition

The POAM II retreival version 6.0 includes the following profile data:

  • Ozone concentration, 15-50 km
  • NO2 concentration, 20-40 km
  • Aerosol extinction at 1060nm, 10-30 km
  • UKMO temperature, pressure, and potential vorticity, 0-60 km

The time span for the data is Nov 3, 1993 to Nov 13, 1996. A complete catalog containing the times and locations of all the retrievals is available below:

Northern Hemisphere Catalog
Southern Hemisphere Catalog

  • Ozone concentration, 5-60 km
  • NO2 concentration, 20-40 km
  • Aerosol extinction at 6 wavelengths, 5-25 km
  • Water Vapour, 5-45 km
  • UKMO temperature, pressure, and potential vorticity, 0-60 km

The time span for the POAM III data is April 22, 1998 to present. A sample catalog containing the times and locations for the first few years of retrievals is available below:

Northern Hemisphere Catalog
Southern Hemisphere Catalog

The data are distributed by FTP in several formats, including ascii format, HDF, and IDL® save files.

The first three satellites were identical and their payloads consisted of two identical HRV (Visible High-Resolution) optical instruments, data recorders (on magnetic tapes), and a system for transmitting the images to the ground-based receiving stations.

SPOT-3 was launched September 26, 1993. The S/C is equipped with 2 HRV imaging sensors, DORIS and POAM-II. While SPOT 1 and SPOT 2 are still operational but SPOT 3 mission interupted by a failure in November of 1996.

The SPOT-4 was taken out of storage and launched on March 24, 1998 on an Ariane-4 vehicle from Kourou. SPOT-4 is considered a 2nd generation satellite. The most important advance is the addition of the "Vegetation" instrument, with four spectral bands to allow continuous, worldwide crop monitoring. The data may be used for crop forecasts and environmental studies.

The SPOT-4 S/C design differs from the earlier SPOT series (SPOT-1,2,3).

Improvements: introduction of electronic sensor gains matching according to landscape type and season, thus ensuring greater dynamic range. In addition, the imaging instruments are no longer susceptible to glare or affected by the polarization of the incident light.

Links

Contact

If you would like to have more information about the POAM data, please contact wdc@dlr.de.