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11-Sep-11 | Delta flight 356 – GRAIL

A Delta II-Heavy lifted off from Florida’s Cape Canaveral Air Force Station on Saturday, 10 September, sending NASA’s Gravity Recovery And Interior Laboratory (GRAIL) mission on its way to the Moon.

A first attempt on Thursday was scrubbed due to upper level wind shear, and Saturday’s launch had to contend with much the same issue: a wind shear at 15–22,000 ft altitude, right around the transsonic region of the Delta II flight path, when the vehicle would be most vulnerable. Fortunately the shear was less severe than Thursday’s and flight controllers were able to work around it, targeting the second of two instantaneous launch windows. The official range liftoff time was 09:08:52.775 EDT.

The twin spacecraft of GRAIL will take nearly four months to reach the Moon, using a circuitous path through the Earth-Sun Lagrange point 1 to help refine and synchronize their orbits to each other. The long cruise will also allow the spacecraft to eliminate any outgassing that could be mistaken for gravitational effects. This will enable them to make highly accurate gravimetric measurements of the Moon in order to map its complete internal structure for the first time in over 50 years of lunar exploration.

According to Jonathan’s Space Report, the Aerojet-built second stage ended up in a 0.88 x 1.05 AU x 0.01 deg heliocentric orbit, with a period of around 347 days. Based on that approximation, the stage could sail past Earth again in 19 years.

The two-stage launch vehicle, with its oversized GEM-46 booster motors marking it as a “Heavy” model, extended the Delta II reputation for reliability, now standing at 95 consecutive successful launches. One Delta II launch—next month’s NPP from Vandenberg—remains on the schedule. United Launch Alliance continues to seek customers for the final 5 Deltas in storage.

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