Total Ozone Mapping Spectrometer (TOMS)

provided by NASA
TOMS logo

Observation Concept

Total Ozone Mapping Spectrometer (TOMS) is an optical sensor to measure the albedo of the earth's atmosphere at six narrow spectral bands. The total ozone content is interrelated with changes of solar radiation in the near ultraviolet wavelengths so that the spatial distribution of the total ozone can be inferred by observing several near UV bands. In addition, the TOMS observation data can be used to make quantitative estimates of sulfur dioxide gases in the near UV band.
The FOV of TOMS is 3 x 3 degrees (swath width : 42 x 42km) and its scanning angle is +/- 55.5 degrees (approx. 2,800km of the ground surface) along the track. This wide swath width can cover the entire earth surface in a day.

Planned Missions

The primary object of TOMS is to collect data of the global ozone content and sulfur dioxide continuously. Combined with monitoring of ozone depletion in the south pole, which has been recently addressed as one of immediate environmental issues, and changes of ozone content after implementation of CFC Protocol, the data can be used for the quantitative analysis of factors related to the ozone issues and the potential effects of volcanic eruptions on climatic changes.

Configuration and Function of Sensor

TOMS consists of optical subsystem, electrical subsystem and driving subsystem.
TOMS overview
TOMS optical system

The scan mirror observes the earth target along cross track direction, and first focuses sun light on the right side of a collimator. The spectrum, using holographic grating, is focused on the other side of the collimator and converted to the electrical signals via optoelectronic amplifier in the focal plan. Each spectrum is focused on the focal plan via Slit Plates and Chopper.
The TOMS observation data will be calibrated by using one of three diffusers. The alternative use is to evaluate degradation of the diffuser by solar radiation. TOMS can also calibrate by using mercury phosphor and wavelength calibration is made by using a reflectance calibrator.

Earth Observation Research Center Earth Observation Research Center
Last Update: 5 Febrary 1998
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