Keeping it Clean: ICON Purge Flow Tests

Under port wing of the L-1011 aircraft looking forward.

Scientific instruments must be kept clean. This is often done by pressurizing the instrument with a clean, dry flow of gas. The clean gas leaks out of any holes and prevents contamination from entering the instrument. This is called purging.

ICON carries four different instruments. The MIGHTI and EUV instruments require a different purge flow rate from that needed by FUV.

Orbital ATK added an additional purge line to their Stargazer L-1011 aircraft specifically for ICON's use.

Under starboard wing looking aft.

In preparation for the launch campaign, tests were run of the new configuration at Stargazer's home base: the Mojave air and spaceport.

Left photo:  Under the port wing of the L-1011 aircraft, looking forward.  This picture shows the Pegasus rocket mount under the belly of the L-1011, the aircraft that will carry the Pegasus rocket that will hold ICON.

Right photo: A supply of nitrogen gas runs through tubes from tanks in the aircraft into the top of the Pegasus mount. There is a slip joint that disconnects when the Pegasus drops at launch. One can see the extension tube hanging down that was used to make testing easier. In the foreground is an instrumented mock-up of the ICON EUV and MIGHTI science instruments. This mock-up was used to measure the gas flow to assure that sufficient purge would be available. A separate mock-up, not shown in this picture, was used for FUV.

[contributed by Will Marchant]