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06-May-02 | Delta flight 291 – Aqua

Following a flawless countdown that NASA’s launch manager characterised as “a snoozer,” Delta flight 291 launched on Saturday, 4 May, to put Aqua into its proper orbit. Official liftoff time was 09:54:58:290 GMT, at the opening of a ten-minute launch window.

This launch of a two-stage Delta 7920-10L was a significant one for Vandenberg AFB. It was the fourth Delta in a row to launch from the west coast range. The only other time this has happened was back in 1971-72, when Delta still had the convenience of working from two launch pads at once. (Space Launch Complex 2-East was decommissioned in 1972; today only the concrete apron remains and the site is used for equipment storage.) In fact, this is the only time SLC-2W has hosted more than two consecutive launches. Kudos to the entire Delta team for their hard work in the wilds of the central California coast.

The flight had a number of other notable aspects. It was the first flight of Boeing’s new stretched-length payload fairing, designated “10L” and three feet longer than the standard 10-foot-diameter composite fairing; it was chosen to accomodate Aqua’s large dimensions. Being a polar-orbit flight, the ground stations used to track the rocket ran the gamut of terrestrial climes, as it passed over McMurdo Sound, Antarctica, Malindi, Kenya, and Thule, Greenland, during its ascent. During a long second-stage coast phase, Aqua’s sensitive instruments required the vehicle to enter a passive thermal control, or “barbeque” roll, to equalize the sun’s heating effects. Finally, spacecraft deployment was performed using an uncommon method to avoid imparting tip-off rates to the payload. Rather than the typical spring-loaded release from the attach fitting, after the retaining clamp and secondary latches were released the Delta second stage used its helium thrusters to slowly back away from the spacecraft.

Aqua, formerly known as EOS-PM, is a NASA orbiter carrying six state-of-the-art instruments to comprehensively study Earth’s water cycle, including “atmospheric temperature and humidity profiles, clouds, precipitation and radiative balance; terrestrial snow and sea ice; sea surface temperature and ocean productivity; [and] soil moisture.” It was originally planned to launch in late 2000, but myriad problems related mainly to spacecraft readiness resulted in cumulative delays of about a year and a half. Over the next four months the satellite will be tested, calibrated, and boosted into a 438 nautical mile operational orbit, before beginning its 6-year science mission.


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