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01-Jul-01 | Delta flight 286 – MAP

Another perfect flight for Delta II as MAP reaches orbit! The 286th Delta launch lifted off from Space Launch Complex 17B at Cape Canaveral Air Force Station on Saturday, 30 June, at 15:46:46.183 EDT. It carried NASA’s Microwave Anisotropy Probe into a nominal, highly elliptical orbit and released the spacecraft about 85 minutes after launch.

MAP is a $145 million mission to map the entire sky in terms of the temperature fluctuations of the cosmic microwave background radiation. It will help to answer questions about the Big Bang theory and galaxy formation that were hinted at by COBE (Delta 189) in 1992.

The spacecraft, following checkout at SAEF-2, was stacked atop the Delta third stage, a Thiokol Star 48B solid-fuel motor, on 15 June. The following week it was packed in its protective canister, transported to SLC-17B and hoisted to the top of the Delta II vehicle. On Tuesday, 26 June, the 10-foot diameter composite payload fairing was installed.

This vehicle, a model 7425-10, is the first example of its type. NASA’s two 1998 Mars probes each used this same three-stage vehicle with four booster motors, but were protected by the standard 9.5-foot steel fairing. The Globalstar launches each used a composite fairing atop a two-stage 7420, which is identical in external appearance to the rocket flown today.

Saturday’s operations began early, as first stage fuelling commenced around 6 a.m. This was prior to Mobile Service Tower rollback and was meant to weigh down and steady the lightweight vehicle against the blustery conditions at the Cape all morning. Even with this precaution, tower cameras showed an occasional, slight rocking motion of the vehicle, while the many umbilical connections swung steadily back and forth in the breeze. Thunderstorms, a common occurrence in the Florida afternoons this time of year, were a concern all day. Launch Weather Officers kept a close eye on a bank of thunderhead clouds hovering north of Orlando, but luckily their anvil tops were not dragged eastward far enough to hold the countdown. Meanwhile, range operations kept a strict perimeter watch against the many pleasure boats out on a warm and mostly sunny weekend day, including a local fishing tournament that (from the sound of it) seemed to stay well clear of the exclusion zone.

The only minor glitch that cropped up in the 150-minute terminal count was due to some noisy data returned during the second stage engine slew tests. Controllers re-ran the tests and determined the noise was in the telemetry and that the yaw actuator was functioning normally. The count was not affected.

Flight 286 lifted off at the opening of its window with its RS-27A main engine, two steering verniers, and all four GEM-40 booster motors firing. The boosters burned out and were jettisoned just over a minute later. The first stage flight time was fairly typical at 4 minutes 35 seconds. The second stage then took over for another 7 minutes, followed by a long, 66-minute coast phase. The second stage restarted briefly for 4 seconds to boost the apogee by about 60 nautical miles, after which the third stage and payload spun up and accelerated for just under 90 seconds. Spacecraft separation came at 87 minutes, 50 seconds into flight, and at T plus 93 minutes the MAP flight team received word that the solar arrays on the probe had successfully deployed.

Over the next few weeks, MAP will fly three highly-elliptical “phasing” orbits as the Moon moves around its orbit to the proper position. Then, in August, MAP will receive a lunar gravity assist that will slingshot the probe to the L2 Lagrange point, a locale of orbital stability a million miles away from Earth in a direct line away from the Sun. While a few spacecraft, including SOHO and ACE (Delta 247), are in orbit around the L1 Lagrange point between the Earth and Sun, MAP marks the first time a spacecraft will attempt to orbit L2.

From there, MAP will continue the research first begun in earnest by COBE, the Cosmic Background Explorer, which launched aboard Delta 189 in 1992 and carried three primary instruments, each of which yielded a major cosmological discovery. MAP’s primary sensor, a bank of passively-cooled radiometers, is a follow-on to COBE’s Differential Microwave Radiometer and will map the complete sky in microwave wavelengths with a sensitivity far surpassing that returned by COBE (in terms of both temperature variation and angular resolution). The results are expected to add evidence for or against several cosmological theories as to the formation and expansion of the universe.


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