Having arrived at Mars on 3 December 1999, the spacecraft would enter the atmosphere, and about 10 minutes prior to landing, would jettison its cruise stage and solar panels and then release the two 3.572 kilogram (each) Deep Space 2 microprobes. Unlike Mars Pathfinder, MPL was scheduled to make a completely controlled landing using retro-rockets all the way to the surface. Landing was scheduled for 21:03 UT on 3 December 1999 with two-way communications planned to begin 20 minutes later. The two Deep Space 2 microprobes (renamed Amundsen and Scott on 15 November 1999), meanwhile, would impact the ground at a speed of 200 meters/second about 50–85 seconds prior to the lander and about 100 kilometers away. Each penetrator was designed to obtain a small sample of subsurface soil using an electric drill for analysis. The microprobes' mission was expected to last about 36 hours while the lander mission would continue until 1 March 2000. Mars Polar Lander successfully left Earth on a Mars transfer trajectory on 3 January 1999. During its traverse to Mars, the spacecraft was stowed inside an aeroshell capsule. The complete vehicle approached Mars in early December in apparently good health. Last contact with the vehicle was at 20:02 UT on 3 December 1999 as the spacecraft slewed to entry attitude. Then, traveling at 6.9 kilometers/second, the capsule entered the Martian atmosphere about 8 minutes later. Controllers expected to reestablish contact 24 minutes after landing (scheduled for 20:14 UT) but no signal was received. With no communications for over two weeks, on 16 December 1999, NASA used the Mars Global Surveyor orbiting Mars to look for signs of the lander on the Martian surface, but the search proved fruitless. On 17 January 2000, NASA finally terminated all attempts to establish contact with the lost lander. An independent investigation into the failure, whose results were released publicly on 28 March 2000, indicated that the most probable cause of the failure was the generation of spurious signals when the lander's legs deployed during the descent. These signals falsely indicated that the spacecraft had touched down on Mars when in fact it was still descending. The main engines prematurely shut down, and the lander fell to the Martian landscape. The demise of MPL undoubtedly set NASA's Mars exploration program back and also spelled the effective end of NASA's "Faster, Better, Cheaper" initiative for low-cost highly innovative missions. The Phoenix lander, which arrived on Mars in 2008, subsequently accomplished most of the original Mars Polar Lander's objectives. MPL carried a CD-ROM with the names of one million children from around the world as part of the "Send Your Name to Mars" program formulated to foster interest in space exploration among young people.
201
Stardust
Nation: USA (76)
Objective(s): comet sample return, comet flybys
Spacecraft: Stardust
Spacecraft Mass: 385 kg
Mission Design and Management: NASA / JPL
Launch Vehicle: Delta 7426-9.5 (no. D266)
Launch Date and Time: 7 February 1999 / 21:04:15 UT
Launch Site: Cape Canaveral Air Force Station / Launch Complex 17A
Scientific Instruments:
-
- dust flux monitor instrument (DFMI)
-
- cometary and interstellar dust analyzer (CIDA)
-
- navigation camera (NC)
-
- stardust sample collection (SSC)
-
- dynamic science experiment (DSE)
Results: Stardust was the fourth of NASA's Discovery program of low-cost exploration missions (after NEAR, Mars Pathfinder, and Lunar Prospector), and the first American mission dedicated solely to studying a comet. It was also the second robotic mission (after Genesis) designed to bring extraterrestrial material from beyond lunar orbit back to Earth. Its primary goal was to fly by the Comet Wild 2 (pronounced "vilt 2"), collect samples of dust from the coma of the comet as well as additional interstellar particles, and then return the samples to Earth. Stardust comprised a 254-kilogram spacecraft that included a 45.7-kilogram return capsule shaped like a blunt-nosed cone. It had five major components: a heat shield, back shell, sample canister, parachute system, and avionics. The samples were to be collected using a low-density microporous silica-based substance known as aerogel, attached to panels on the spacecraft to "soft-catch" and preserve the cometary materials. The spacecraft was launched into heliocentric orbit that would bring it around the Sun and past Earth for a gravity-assist maneuver to direct it to Wild 2 after a flyby of the minor planet Annefrank in November 2002. After mid-course corrections on 28 December 1999, 18 January, 20 January, and 22 January 2000, its first interstellar dust collection operation was carried out between 22 February and 1 May 2000. After approximately a year in heliocentric orbit, Stardust flew by Earth (at a range of 6,008 kilometers) on 15 January 2001 for a gravity assist to send it on a second sample collection exercise between July and December 2002. On 2 November 2002 at 04:50 UT, Stardust flew by asteroid 5535 Annefrank at a range of 3,078 kilometers. During the encounter, the spacecraft's dust collectors collected samples while its camera returned 72 images. Over a year later, on 31 December 2003, the spacecraft entered the coma of Comet Wild 2 (or 81P/Wild) with the closest encounter (at a range of 250 kilometers) taking place at 19:22 UT on 2 January 2004. The sample collector, which had been deployed on 24 December was retracted about 6 hours after closest approach, stowed, and then sealed in the "sample vault." The imaging system also took 72 images of the comet's nucleus. Exactly as planned, after a 4.63 billion-kilometer trip lasting over two years, at 05:57 UT on 15 January 2006, Stardust's Sample Return Capsule (SRC) separated from the main vehicle and, 4 hours later, entered Earth's atmosphere. Slowed down by the drogue and main parachutes, the capsule landed at 10:10 UT within a 30 × 84-kilometer landing zone at the U.S. Air Force Test and Training Range in Utah. Because of high winds, the capsule drifted north of the ground track, but fortunately a locator beacon allowed rescuers to find the capsule 44 minutes after landing. The capsule had returned more than 10,000 particles larger than 1 micrometer from Wild 2. The main spacecraft, meanwhile was diverted so as not to reenter Earth's atmosphere. At 06:13 UT on 15 January, it fired its engines, flew past Earth and then the Moon before entering hibernation mode on 29 January 2004 and remains in a 3-year-long heliocentric orbit. In July 2007, NASA approved an extended mission for Stardust known as New Exploration of Tempel 1 (NExT) that envisaged a flyby of Comet Tempel 1 (or 9P/Tempel), which had been the target for Deep Impact's impact probe in 2005. The spacecraft, now known as Stardust/NExT, flew by Tempel 1 at 04:42:00 UT on 15 February 2011 at a range of 181 kilometers, returning 72 images of the nucleus. This was the first time a comet had been revisited. It was also during this flyby that investigators were able to conclusively identify the impact crater from Deep Impact's Impactor probe. Stardust carried out a final engine burn on 24 March 2011 exhausting all of its propellant. It sent its last transmission at 12:33 UT the same day, ending an 11-year mission. The analysis of the samples returned showed the presence of a wide range of organic compounds. In August 2014, NASA announced that seven rare, microscopic interstellar dust particles dating from the very origins of the solar system were among the samples collected by Stardust.
202
2001 Mars Odyssey
Nation: USA (77)
Objective(s): Mars orbit
Spacecraft: 2001 Mars Odyssey
Spacecraft Mass: 1,608.7 kg
Mission Design and Management: NASA / JPL
Launch Vehicle: Delta 7925-9.5 (no. D284)
Launch Date and Time: 7 April 2001 / 15:02:22 UT
Launch Site: Cape Canaveral Air Force Station / SLC-17A
Scientific Instruments:
-
- thermal emission imaging system (THEMIS)
-
- gamma ray spectrometer (GRS)
-
- Mars radiation environment experiment (MARIE)
Results: As of mid-2017, 2001 Mars Odyssey holds the record for the longest surviving continually active spacecraft in orbit around a planet other than Earth, at 16 years and counting. This, the first launch in NASA's revamped Mars Exploration Program (which was originally approved in 1993 but restructured in October 2000 after the failures associated with "Faster, Better, Cheaper"), was designed to investigate the Martian environment, providing key information on its surface and the radiation hazards future explorers might face. The goal was to map the chemical and mineralogical makeup of Mars as a step to detecting evidence of past or present water and volcanic activity on Mars. It was also designed to act as a relay for future landers, and did so for the Mars Exploration Rovers (Spirit and Opportunity), the Mars Science Laboratory, and the Phoenix lander.
<!-- image -->During the coast to Mars, in August 2001, the MARIE radiation instrument failed to respond but was successfully revived by March 2002. About 200 days after launch, at 02:38 UT on 24 October 2001, Mars Odyssey successfully entered orbit around Mars after a 20-minute, 19-second-long engine burn. The initial orbit was highly elliptical (272 × 26,818 kilometers), taking the spacecraft 18.6 hours to complete one circuit. The spacecraft then implemented an unusual aerobraking maneuver that used the planet's atmosphere to gradually bring the satellite closer to the Martian surface on every succeeding orbit. This process saved an estimated 200 kilograms of propellant. Once the aerobraking was over, by 30 January 2002, Mars Odyssey was in its nearly Sun-synchronous polar orbit of 400 × 400 kilometers at 93.1° inclination, allowing the initiation of its science and mapping mission on 19 February 2002. This phase lasted 917 Earth days during which entire ground tracks were repeated every two sols. One of the most exciting findings of Mars Odyssey came early on in the mission. In May 2002, NASA announced that the probe had identified large amounts of hydrogen in the soil, implying the presence of ice possibly a meter below the planet's surface. Much later, in March 2008, mission scientists revealed that Mars Odyssey had found evidence of salt deposits in 200 locations in southern Mars. These chloride minerals were left behind as places where water was once abundant. Having fully completed its primary mission by August 2004, mission planners began a series of extended missions starting 24 August 2004. NASA approved seven two-year extensions of the Mars Odyssey mission, in 2004, 2006, 2008, 2010, 2012, 2014, and 2016. Each was dedicated to a specific set of objectives. For example, the fourth extension ending in August 2012 was dedicated to observing the year-to-year variations in polar ice, clouds, and dust storms. One of its instruments, the MARIE radiation experiment, stopped working on 28 October 2003, after a large solar event bombarded the spacecraft early in the mission, most likely because of a damaged computer chip. In addition, one of the spacecraft's reaction wheels failed in June 2012, but a spare, installed on board as a redundancy, was activated and spun into service a month later. A few months later, in August 2012, NASA used Mars Odyssey's THEMIS instrument to help select a landing site for the Mars Science Laboratory (MSL) and later acted as a relay for the MSL rover Curiosity. By July 2010, NASA was able to announce that Mars Odyssey's camera had helped construct the most accurate global map of Mars ever, using 21,000 images from the THEMIS instrument. These pictures have been smoothed, matched, blended, and cartographically controlled to make a giant mosaic available to users online. Later that year, on 15 December 2010, Mars Odyssey claimed the record for the longest operating spacecraft at Mars, with 3,340 days of operation. In December 2016, the spacecraft put itself into "safe mode" due to a problem with orientation relative to Earth and the Sun but by early January 2017 was restored to full operating status. During its many years in Martian orbit, Mars Odyssey globally mapped the amount and distribution of the numerous chemical elements and minerals in the Martian surface and also tracked the radiation environment in low Mars orbit, both necessary before humans can effectively explore the Martian surface. By mid-2016, the THEMIS instrument had returned more than 208,000 images in visible-light wavelengths and more than 188,000 in thermal-infrared wavelengths.