234 MAVEN
Nation: USA (99) Objective(s): Mars orbit Spacecraft: MAVEN Spacecraft Mass: 2,454 kg Mission Design and Management: NASA / GSFC / University of Colorado-Boulder Launch Vehicle: Atlas V 401 (AV-038 + Centaur) Launch Date and Time: 18 November 2013 / 18:28:00 UT Launch Site: Cape Canaveral Air Force Station / SLC-41
Scientific Instruments:
- P&F particle and fields package a. solar wind electron analyzer (SWEA) b. solar wind ion analyzer (SWIA) c. supra thermal and thermal ion composition (STATIC) d. solar energetic particle experiment (SEP) e. Langmuir probe and waves experiment (LPW) f. magnetometer (MAG)
- RS remote sensing package a. imaging ultraviolet spectrometer (IUVS)
- NGIMS neutral gas and ion mass spectrometer package
Results: The Mars Atmosphere and Volatile Evolution (MAVEN) mission was selected as part of NASA's now-cancelled Mars Scout Program to explore the atmosphere and ionosphere of the planet and their interaction with the Sun and solar wind. The goal is to use this data to determine how the loss of volatiles from the Martian atmosphere has affected the Martian climate over time, and thus contribute to a greater understanding of terrestrial climatology. The Mars Scout Program involved low cost spacecraft (less than $450 million) but was cancelled in 2010 after approval of MAVEN and the Phoenix lander. Further Mars missions would now be selected competitively under the Discovery Program. Because of a U.S. Government shutdown in the fall of 2013, MAVEN nearly didn't get off the ground. Fortunately, MAVEN was defined as part of "critical infrastructure," allowing the launch to proceed on time on 18 November 2013.
Engineers and technicians test deploy the two solar panels on NASA's MAVEN spacecraft. The image was taken in the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center before launch in November 2013. Credit: NASA/ Kim Shiflett
<!-- image -->The payload successfully reached a 167 × 315-kilometer parking orbit around Earth (at 26.7° inclination). Soon, the Centaur upper stage (with its RL-10A-4-2 engine), fired the spacecraft into a hyperbolic Earth orbit at 195 × 78,200 kilometers at 27.7° inclination. On 21 November, another burn inserted the spacecraft on a Trans-Mars trajectory, with further mid-course corrections on 3 December 2013 and 27 February 2014. At 03:24 UT on 21 September 2014, MAVEN successfully entered orbit around Mars after a 10-month journey when its six main engines fired, two by two in succession, and burned for 33 minutes and 26 seconds to slow the craft. The spacecraft entered a six-week commissioning phase before beginning science operations. The initial orbital period was 35.02 hours. The primary mission, in an orbit with a period of 4.5 hours, included five "deep-dip" campaigns, during which MAVEN's periapsis was lowered from 150 kilometers to about 125 kilometers to collect data on the boundary between the upper and lower atmosphere. By mid-October all of its scientific instruments were turned on. Because of the close Martian flyby (about 139,500 kilometers) of Comet C/2013 A1 (Siding Spring) on 19 October, controllers took precautions to protect MAVEN from damage. In the event, MAVEN survived without any damage, and also returned valuable data on the comet's effects on the Martian atmosphere. MAVEN began its one-year primary science mission on 16 November, carrying out regular observations of the Martian upper atmosphere, ionosphere, and solar-wind interactions with its nine scientific instruments. MAVEN completed the first of its five "deep-dip" maneuvers between 10 and 18 February 2015. As with most of these dives, the first three days were used to lower the periapsis, with the remaining five days used for scientific investigations over roughly 20 orbits. Given that the planet rotates under the spacecraft, the 20 orbits allow the opportunity to explore different longitudes spaced around Mars, essentially giving it a global reach. The following month, based on data collected in December 2014, mission scientists announced that they had detected two unanticipated phenomena in the Martian atmosphere, one involving a high-altitude dust cloud (at about 150–300 kilometers altitude) and the other, a bright ultraviolet auroral glow in the northern hemisphere. Like all the other probes in orbit or on the surface of Mars, communications with MAVEN were put on hold during the Mars conjunction in June 2015. MAVEN commemorated a year in orbit in September 2015 by which time it had carried out four deep dive campaigns. By this time, NASA had approved an extended mission past November. In a major reveal in November 2015, scientists published the results (in the journals Science and Geophysical Research Letters) of their analysis of data from MAVEN, which identified the processes that contributed to the transition of the Martian climate from an early, warm, and wet environment that might have supported surface life to the cold and dry world at the present. More specifically, the information helped to determine the most accurate rate at which the Martian atmosphere was currently losing gas to space via "stripping" to the solar wind. In late November and early December 2015, MAVEN made a series of close flybys of Phobos, coming within 500 kilometers of its surface, and collecting spectral images using the IUVS instrument. On 3 October 2016, MAVEN completed an entire Mars year of scientific observations. The following year, on 28 February 2017, MAVEN carried out a small orbital maneuver, the first of its kind, to avoid a possible impact with Phobos. During MAVEN's second Martian year in orbit, through 2017, research was being coordinated with simultaneous atmospheric observations by ESA's Trace Gas Orbiter.
235 Chang’e 3 and Yutu
Nation: China (4) Objective(s): lunar landing and rover Spacecraft: Chang’e sanhao Spacecraft Mass: 3,780 kg (140 kg Yutu) Mission Design and Management: CNSA Launch Vehicle: CZ-3B (no. Y23) Launch Date and Time: 1 December 2013 / 17:30 UT Launch Site: Xichang / Launch Complex 2
Scientific Instruments:
Lander:
- terrain camera (TCAM)
- landing camera (LCAM)
- Moon-based ultraviolet telescope (MUVT)
- extreme ultraviolet camera (EUVC)
Yutu:
- panoramic camera (PCAM)
- lunar penetrating radar (LPR)
- imaging spectrometer (VIS-NIR)
- active particle induced x-ray spectrometer (APXS)
Results: Launched as part of the second phase of the Chinese Lunar Exploration Program, Chang'e 3 was the most sophisticated robotic probe launched by the Chinese to date. The spacecraft included a four-legged soft-lander and a small rover named Yutu ("Jade Rabbit") to traverse the lunar surface. The 765-kilogram lander was based around an octagon-shaped body with four legs, a throttleable engine at the bottom, refoldable solar panels, a radioisotope heater unit to generate heat, and three engineering monitoring cameras at the top. The lander's mission lifetime was one year. Besides the technological objectives of the mission, the lander and rover also had some scientific objectives including investigating the lunar topography and geological structure of the Moon; studying the material composition of the lunar surface; surveying the space environment between the Moon, Earth, and Sun; and carrying out astronomical observations from the lunar surface. The launch was marred by hardware from the rocket that landed on villages downrange from the launch site, although no one was hurt.
Image taken on 13 January 2014 by the panoramic camera (PCAM) on board the Chinese Yutu lunar rover as it looked back at the Chang'e 3 lander. Credit: Chinese Academy of Sciences / China National Space Administration / The Science and Application Center for Moon and Deepspace Exploration / Emily Lakdawalla
<!-- image -->The payload was inserted directly into a lunar transfer orbit of 210 × 389,109 kilometers at 28.5° inclination. After two mid-course corrections (on 2 and 3 December), the spacecraft fired its engine at 09:41 UT for 6 minutes and entered a 100-kilometer circular orbit around the Moon. On 10 December, Chang'e 3 lowered its orbit to a 15 × 100-kilometer orbit. When it reached perilune on 14 December, its engine fired at 13:00 UT for a powered descent to the lunar surface (apparently one orbit earlier than planned, probably to ensure a live broadcast on Chinese TV). The 11-minute landing sequence was punctuated by a "hazard avoidance maneuver" about 100 meters above the surface. The main engine cut out at 4 meters above the surface, and the lander settled down naturally the rest of the way, landing at 13:11 UT, thus becoming the first spacecraft to soft-land on the Moon since the Soviet Luna 24 in 1976.
Image taken on 17 December 2013 by the Lander Terrain Camera (TCAM) on board the Chinese Chang'e 3 lander showing the Yutu rover on the surface of the Moon. Credit: Chinese Academy of Sciences / China National Space Administration / The Science and Application Center for Moon and Deepspace Exploration / Emily Lakdawalla
<!-- image -->Landing coordinates were announced as 19.51° W / 44.12° N, in the northwestern portion of Mare Imbrium which, as it turns out was different than what was announced earlier—Sinus Iridum. Immediately after landing, Chang'e 3 deployed its solar panels. Soon, a command was sent to Yutu to deploy its two solar panels and unlock its wheels. Yutu was a 6-wheeled mobile spacecraft capable of transmitting video in real time and able to perform relatively simple soil analyses. Like the lander, the rover had its own radioisotope heater units (using plutonium-238) for heating. It also had sensors that enabled it to automatically negotiate over obstacles on the surface. Its original planned lifetime was three months, during which it was expected to travel an area of 3 square kilometers. At 20:10 UT on 14 December, the rover began to slowly move toward the rover transfer mechanism, which then slowly lowered itself until its tracks touched the lunar surface. At 20:35 UT, the rover wheeled down and touched the surface. The rover remained at Point A, about 10 meters north of the lander for about 13 hours until it turned around and cameras on the rover and lander took pictures of each other on 15 December. The rover then slowly moved to Point B and entered into sleep mode for four days. Woken up on 20 December, Yutu traveled about 21 meters from Point B to C and then to Point D, testing its robotic arm on 23 December. Both lander and rover entered into hibernation mode on 25 and 26 December, respectively, in anticipation of the lunar night. On 11–12 January the lander and Yutu were brought out of sleep to begin their second lunar day. The rover, however, ran into a major problem later in the month; on 25 January, the Chinese media announced that Yutu had suffered a "mechanical control anomaly" caused by the "complicated lunar surface environment." Because the problem occurred just before the rover was entering hibernation for its second lunar night, controllers had to wait until hibernation was over to confirm the problem. After failing to hear from the rover on 10 February, ground controllers established contact two days later but it was clear at this point that Yutu was no longer capable of moving across the lunar surface, apparently because of a control circuit malfunction in its driving unit. Instead, mission scientists reformulated a limited mission for Yutu as a stationary science platform. Total traverse distance was computed as 0.114 kilometers. Because the problem on the rover was in a unit that also controlled the mobility of the solar panels to face the Sun, controllers expected the rover to lose power, but the rover appears to have communicated with mission control through at least early September 2014. The lander meanwhile entered a "maintenance mode" at some point in mid-2014 but continued operating through the year. In January 2015, over a year after landing, the Chinese media announced that the lander was still returning data, having entered its 14th lunar night, thus making it the longest functioning spacecraft on the lunar surface. The lander was said to be in contact at least once a month well into fall 2016 and sending back scientific data from at least one instrument, its ultraviolet telescope. The Chinese also released entire datasets of imagery from both the lander and the rover in January 2016. As far as Yutu, in March 2015, Ye Peijian confirmed that the rover was immobile but still working. The rover was still maintaining communications to at least July 2016 but the following month, Yutu was officially declared dead after operating for 31 months. At least one instrument on the lander (the ultraviolet telescope) was still active as of June 2018.