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Shuttle Radar Topography Mission




The SRTM instrument was made up of three sections, the main radar antenna, the mast, and the outboard radar antenna.

Wire diagram of main antenna, mast, outboard antenna SRTM instrument carried through the air via tug and crane at KSC.

Drawing of main antenna in stowed configuration
The Main Antenna

The main radar antenna transmitted the radar pulse. It contained special panels that allowed it to receive the returned radar pulse after it bounced off the Earth. It was attached to a structure that was bolted into the payload bay of the space shuttle.

The Mast

The mast was folded up accordian-style inside a canister that was attached to the side of the main antenna. After the shuttle was in space and the payload bay doors opened, the mast emerged from the canister and extended out to 60 meters (200 feet). The SRTM mast is longest rigid structure ever flown in space.

Mast Image
Mast fully extended from canister at AEC-Able

Outboard antenna attached to canister for shuttle fligh
The Outboard Antenna

The outboard antenna was attached to the end of the mast. While inside the payload bay, the outboard antenna was folded along the top of the canister and the main antenna. After the payload bay doors opened but before the mast was extended, the outboard antenna was partially swung down. After the mast fully extended, the outboard antenna was lowered into its operating position. The outboard antenna contained special panels that allowed it to receive the same returned pulse as the main antenna.

Photo of Earth
A Near-Global Topographic Map

The radar data the SRTM instrument captured will allow us to create very detailed topographic maps of the Earth's surface using a technique called interferometry. Interferometry is the study of interference patterns caused by radar signals received at two different antennas. The SRTM instrument was designeded to capture one signal using two antennas. Because it flew around the Earth, SRTM will create maps on a global scale. It even mapped places on the Earth that have never been mapped before. The SRTM instrument will create the most complete global topographic map ever made.