Beyond_Earth-_A_Chronicle_of_Deep_Space_Exploration_1958-2016.pdf

203

Microwave Anisotropy Probe (MAP)

Nation: USA (78)

Objective(s): Sun–Earth L2 Lagrange Point

Spacecraft: Explorer 80

Spacecraft Mass: 840 kilograms

Mission Design and Management: NASA / GSFC

Launch Vehicle: Delta 7425-10 (no. D286)

Launch Date and Time: 30 June 2001 / 19:46:46 UT

Launch Site: Cape Canaveral Air Force Station / SLC-17B

Scientific Instruments:

• 1. Pseudo-Correlation Radiometer (fed by two back-to-back reflectors)

Results: The Microwave Anisotropy Probe was designed to map the relative Cosmic Microwave Background (CMB) temperature with high angular resolution and sensitivity over the full sky. In order to achieve this, MAP used differential microwave radiometers that measured temperature differences between two points on the sky from its operational position at the Sun–Earth L2 Lagrange Point, about 1.5 million kilometers from Earth. The two back-to-back telescopes were designed to focus microwave radiation from two spots on the sky approximately 140° apart and feed it to 10 separate differential receivers. The MAP mission was a successor to the Cosmic Background Explorer (COBE) mission, also known as Explorer 46, launched in 1989. The spacecraft was launched into an initial orbit of 167 × 204 kilometers at 28.8° inclination. A third stage burn directed MAP into a highly elliptical orbit at 182 × 292,492 kilometers at 28.7° degrees. After three large elliptical loops around Earth, the spacecraft flew by the Moon on 30 July and arrived at the Sun–Earth L2 on 1 October 2001. Its position at L2 minimizes the amount of contaminating solar, terrestrial, and lunar emissions while also ensuring a stable thermal state. At L2, MAP was in a 6-month Lissajous orbit. In 2003, MAP was renamed the Wilkinson Microwave Anisotropy Probe (WMAP) in honor of cosmologist and mission scientist David Todd Wilkinson (1935–2002) who passed away the year before. Since its operational mission began, NASA has issued public "data releases" in 2003, 2006, 2008, 2010, and 2012 that have added an immense amount of rich information to our understanding of the origins of the universe. First and foremost, WMAP's data played a major role in precisely confirming the origin, content, age, and geometry of the universe. Among its many findings has been: the first fine-resolution (0.2 degree) full-sky map of the microwave sky; a more precise determination of the age of the universe (13.77 billion years); more accurate data on the curvature of space; data that has allowed scientists to reduce the volume of cosmological parameters by a factor of over 68,000; and the discovery that dark matter and dark energy (in the form of the cosmological constant) make up about 24.0% and 71.4% of the universe, respectively. All of these findings and others cumulatively provided more confirmation for the prevailing standard model of Big Bang cosmology, the Lambda-CDM model. After 9 years of operation, in October 2010, the WMAP spacecraft was moved to a derelict heliocentric graveyard orbit outside L2 where the probe will circle the Sun once every 15 years.

204

Genesis

Nation: USA (79)

Objective(s): solar wind sample return, Sun–Earth L1 Lagrange Point

Spacecraft: Genesis

Spacecraft Mass: 636 kg

Mission Design and Management: NASA / JPL

Launch Vehicle: Delta 7326-9.5 (no. D287)

Launch Date and Time: 8 August 2001 / 16:13:40 UT

Launch Site: Cape Canaveral Air Force Station / SLC-17A

Scientific Instruments:

• 1. solar wind ion monitor
• 2. electron monitor

Results: During its nearly two years in halo orbit around the Sun–Earth L1 point, the Genesis, the fifth Discovery-class spacecraft, was designed to collect samples of the solar wind and then subsequently return them to Earth. The collection device, fixed inside the return capsule, was made of a stack of four circular metallic trays, one that would be continuously exposed, and the other three deployed depending on particular solar wind characteristics. After insertion into a low parking orbit around Earth, the third stage fired exactly an hour after launch, at 17:13 UT on 8 August 2001 to send the spacecraft towards its destination at L1. On 16 November, a 4-minute 28-second burn of its engine put Genesis into a halo orbit around L1 with a radius of about 800,000 kilometers and a period of six months. The first array was exposed for sample collecting a little over two weeks later on 30 November, while the others, depending on the particular array, were left exposed from 193 days (coronal mass ejection collector) to 887 days (the bulk arrays). The prior record for a solar wind collector (on Apollo 16 in 1972) had been a short 45 hours. All the trays were stowed away on 1 April 2004, and exactly three weeks later, on 22 April, the spacecraft fired its four thrusters and began its long trek back via an unusual trajectory that took it past the Moon (at a range of 250,000 kilometers), Earth (at 392,300 kilometers), and then to L2, which it reached in July 2004. Swinging around L2 it headed in the direction of Earth. About 5.5 hours prior to reentry on 8 September, the spacecraft bus ejected its return capsule and then fired its thrusters to enter a parking orbit around Earth partly as a precaution in case separation had not occurred. The capsule successfully separated and hit Earth's atmosphere, experiencing a force of 27 g's. The drogue parachute (which would have deployed the main chute) unfortunately did not deploy, and the capsule hit the ground at an estimated speed of 311 kilometers/hour at 15:58 UT on 8 September 2004. The "landing" was, as designed, in the Dugway Proving Ground in the Utah Test and Training Range, but obviously the capsule was severely damaged and contaminated. The shattered sample canister was taken to a clean room and, over the subsequent month, disassembled carefully. Teams eventually tagged 15,000 fragments of the return capsule. Despite the condition of the capsule, over a period of several years, project scientists were able to glean a significant amount of data from the recovered debris and published results detailing, for example, the identification of argon and neon isotopes in samples of three types of solar wind captured by the spacecraft. An investigation into the accident found that the drogue failed to deploy due to a design defect that allowed an incorrect orientation during assembly of gravity-switch devices that initiate deployment of the spacecraft's drogue parachute and parafoil. The main Genesis bus meanwhile headed back to L1 and then entered heliocentric orbit. Contact was maintained until 16 December 2004.

205

CONTOUR

Nation: USA (80)

Objective(s): comet flyby

Spacecraft: Contour

Spacecraft Mass: 970 kg

Mission Design and Management: NASA / APL

Launch Vehicle: Delta 7425-9.5 (no. D292)

Launch Date and Time: 3 July 2002 / 06:47:41 UT

Launch Site: Cape Canaveral Air Force Station / SLC-17A

Scientific Instruments:

• 1. remote imager/spectrograph (CRISP)
• 2. forward imager (CFI)
• 3. neutral gas ion mass spectrometer (NGIMS)
• 4. dust analyzer (CIDA)

Results: This sixth Discovery-class mission (after Mars Pathfinder, NEAR, Lunar Prospector, Stardust, and Genesis) was designed to fly by at least two cometary nuclei with the goal of compiling topographical and compositional maps, sending back imagery, and collecting data on the structure and composition of their comas.

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Named Comet Nucleus Tour (CONTOUR), the spacecraft would carry out its principal mission from heliocentric orbit with encounters with Comet 2P/Encke (on 12 November 2003), 73P/Schwassmann-Wachmann-3 (on 19 June 2006) and possibly, 6P/d'Arrest (16 August 2008). The spacecraft was successfully launched into a high apogee orbit (with a period of five-and-a-half days). Controllers implemented at least 23 orbital maneuvers over the next 43 days (and 25 orbits) to position CONTOUR properly for its planned burn to heliocentric orbit on 15 August. On that day, at 08:49 UT, its solid propellant apogee motor fired as the spacecraft was approaching perigee over the Indian Ocean and out of radio contact. Unfortunately, nothing was ever heard from CONTOUR again. Later investigation showed that the spacecraft had broken up during its burn. The spacecraft probably suffered structural failure due to "plume heating" as its main engine was firing, caused either by problems in the design of the probe or the solid rocket motor itself.

206

Hayabusa

Nation: Japan (5)

Objective(s): asteroid sample return

Spacecraft: MUSES-C + MINERVA

Spacecraft Mass: 510 kg

Mission Design and Management: ISAS / JAXA

Launch Vehicle: M-V (no. 5)

Launch Date and Time: 9 May 2003 / 04:29:25 UT

Launch Site: Kagoshima / M-V

Scientific Instruments:

• 1. light detection and ranging instrument (LIDAR)
• 2. near infrared spectrometer (NIRS)
• 3. x-ray fluorescence spectrometer (XRS)
• 4. wide-range camera (ONC-W)
• 5. telescopic camera (AMICA)
• 6. four ion thrusters

Results: With this mission, Japan hoped to be the first nation to visit a minor planet and return samples from it. The plan was for the spacecraft to launch in 2003, encounter its target in 2005, and then return to Earth, with a landing in the Woomera Test Range in South Australia in 2007. NASA had originally planned to supply a nano-rover for the mission but backed out from the mission in November 2000. Instead, ISAS built its own rover, called MINERVA (Micro/Nano Experimental Robot Vehicle for Asteroid), a 16-sided "hopper" that weighed only 600 grams and was equipped with six thermometers, a pair of stereoscopic cameras, and a short-focus camera. MUSES-C, named Hayabusa (or "Peregrine falcon") after launch, lifted off with MINERVA and was inserted directly into a solar orbit of 0.860 × 1.138 AU. Its goal was to rendezvous with asteroid 1998SF36 (now renamed Itokawa after the founding figure of the Japanese space program).

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During its outbound trip, controllers operated its ion engines, although one (of a total of four) failed soon after launch. As per its mission profile, the spacecraft returned towards Earth for a gravity assist flyby on 19 May 2004 at a range of 3,725 kilometers and then moved into a 1.01 × 1.73 AU heliocentric orbit. Unfortunately, right after this, Hayabusa was caught in the aftermath of a massive solar eruption that degraded its solar cells (and thus power to its ion engines). Mission managers scrambled to come up with a new schedule, delayed now for both the asteroid encounter and return to Earth. As it approached in the direction of Itokawa, the spacecraft's ion engines (one of which had operated for 10,400 hours) were shut off, and its main engine fired at 01:17 UT on 12 September 2005 to terminate its "approach phase." At the time, it was only 20 kilometers from its target. In its station-keeping mode, Hayabusa took hundreds of high resolution pictures, but by 3 October, two of its three reaction wheels controlling the attitude had failed. Yet, the spacecraft was able to conduct two "rehearsal" landings (on 4 and 9 November). During a third rehearsal, at a distance of about 55 meters, controllers commanded the mother ship to release MINERVA. Because tracking was being transferred from a Japanese antenna to a NASA one, key information was lacking about Hayabusa's vertical speed. By the time the command reached Hayabusa, it was actually moving away at 15 meters/second. As a result, MINERVA missed its target and flew into heliocentric orbit. Remarkably, the little rover operated as planned for 18 hours. On 19 November, the main spacecraft successfully executed a descent run and landed softly at 21:09:32 UT at 6° S / 39° E in the middle of a feature named "MUSES Sea." The probe rebounded but settled down in a stable position by 21:41 UT. (The spacecraft was preceded by one of three target markers that had the names of 880,000 people engraved on it). The spacecraft was, however, not properly aligned and took off at 22:15 UT in what was the first ever liftoff from a celestial body apart from Earth or the Moon. During a second landing at 22:07 UT on 25 November, the spacecraft was supposed to fire two small projectiles to generate a spray of soil for collection, but later data indicated this probably did not occur, although some material was clearly collected. Hayabusa immediately lifted off again, although it had suffered some damage during landing that caused a propellant leak in the attitude control system. This caused a cascade of problems including loss of solar orientation necessary for the spacecraft to have any power. With contact becoming rather intermittent, on 8 December tracking stations noted an abrupt change in attitude and a decrease in signal strength. At this point, Hayabusa was tumbling. Remarkably, controllers re-established contact (presumably after the tumbling had ceased when the leaking propellant had run out) on 23 January 2006. The spacecraft's condition was dire but JAXA was able to revive a number of systems. A year later, on 17–18 January 2007, the lid of the sample catcher was closed, and the catcher stowed into the return capsule. Finally, a plan to use its ion thrusters to return it to Earth was implemented: on 25 April 2007, two ion engines began to fire, continuing for about seven months. A second firing period began on 4 February 2009, designed to bring the spacecraft back to Earth. By this time, only one of the four thrusters was operable, which itself failed in November, leaving Hayabusa four months short of the firing time needed to get back to Earth. Japanese engineers came up with an ingenious solution, to use the ion source from one engine (engine B) with the neutralizer from another (engine A). The final phase of operation of the ion thruster concluded on 27 March 2010, followed by four short course corrections. On 13 June 2010, at a range of 40,000 kilometers from Earth, the spacecraft released its return capsule, just 3 hours before reaching Earth's atmosphere. Both entered the atmosphere at 13:51 UT and began to decelerate. While the mother ship burned up as expected, the return capsule was unscathed. It deployed its parachute and landed just 500 meters from its target point in the Woomera Test Range in Australia at 14:12 UT and was successfully recovered soon after. In November 2010, Japanese scientists announced that the return capsule had indeed returned 1,500 grains of rock (most smaller in size than 10 micrometers) from Itokawa, this being the second sample (after that from Genesis) returned from another celestial body other than the Moon.