Originally, the data obtained from Earth Probe (EP-) TOMS were intended to complement data obtained from ADEOS TOMS, which gave complete equatorial coverage due to its higher orbit. EP-TOMS was launched into a 500 kilometer orbit rather than the originally planned 950 kilometer orbit. The lower orbit decreased the size of the "footprint" of each measurement, which increased the resolution and also increased the ability to make measurements over cloudless scenes. This orbit was chosen to improve the ability of the TOMS instrument to make measurements of UV-absorbing aerosols in the troposphere. Tropospheric aerosols play a major role in the Earth's climate and the capability to measure them from a TOMS instrument ha recently been developed using data from Nimbus-7 and Meteor-3 TOMS.

The increased probability of making measurements over cloud-free areas enhanced the capability of converting the TOMS aerosol measurements into geophysical quantities such as optical depth. Although the lower orbit precluded full global coverage in the equatorial region, the scanning range of the TOMS instrument still provided full coverage over the poles. EP-TOMS would have still been able to completely track and map the development of the Antarctic ozone hole and the springtime decrease of ozone in the northern hemisphere.

However, ADEOS failed in June 1997. The orbit of EP has been boosted to 740 km and circularized to provide coverage that is as complete as possible. As with the pre-boosted measurements, the EP-TOMS data still has missing elements at the equator, but these do not present a significant problem in analysis.

Current orbital characteristics (as of 12/13/97): Altitude : 740 km Inclination : 98.385 deg Period : 99.65 min EP-TOMS FOV at nadir : 39 km latitude x 39 km longitude	Original orbital characteristics (before 12/5/97): Apogee Altitude : 515.2 km Perigee Altitude : 490.5 km Orbit Inclination : 97.432 deg. Period : 94.6 min EP-TOMS FOV at nadir : 26 km latitude x 26 km longitude
There are no EP TOMS data between (12/05/1997 - 12/10/1997)* and (12/13/1998 - 01/02/1999)*, The EP-TOMS instrument technical specifications Here is the EP-TOMS Data Product User's Guide (in PDF format) Pre-launch Technical Information about the Earth Probe spacecraft Prelaunch images of the spacecraft and the Pegasus launch vehicle Here is a summary and a fact sheet explaining the original Earth Probe TOMS mission.	Here's the official Earth Probe TOMS mission patch (98 Kbytes) Note: A 200 dpi version of the mission patch is also available (437k)
	Check out EP-TOMS data and images.

* Date in mm/dd/yyyy format