236 Gaia
Nation: ESA (8) Objective(s): Sun–Earth L2 Lagrange Point Spacecraft: Gaia Spacecraft Mass: 2,029 kg Mission Design and Management: ESA Launch Vehicle: Soyuz-ST-B / Fregat-MT (Soyuz-ST-B no. E15000-004/104, Fregat-MT no. 1039) Launch Date and Time: 19 December 2013 / 09:12:18 UT Launch Site: CSG / ELS pad
Scientific Instruments:
- astrometric instrument (ASTRO)
- photometric instrument
- radial velocity spectrometer (RVS)
Results: Gaia is a European space observatory whose goal is to chart a three-dimensional map of the Milky Way galaxy in order to reveal the composition, formation, and evolution of the galaxy. More specifically, Gaia provides high-quality positional and radial velocity measurements to produce a stereoscopic and kinematic census of about one billion stars in our galaxy (about 1% of the total) and the Local Group. Launched by a Russian Soyuz, the Fregat upper stage pushed Gaia into a 175 × 175-kilometer Earth orbit, and then fired again for a long burn into a 344 × 962,690-kilometer orbit at 15.0° inclination. It performed a mid-course correction the day after launch. On 8 January 2014, Gaia entered its operational orbit around the Sun–Earth L2, about 1.5 million kilometers from Earth, when its engine fired to boost the spacecraft into a 263,000 × 707,000-kilometer halo orbit around L2 with a period of 180 days. After four further months of calibration, alignment, and proper focusing of the telescopes on board, Gaia began its five-year mission on 25 July 2014 to produce the most accurate 3D map of the Milky Way galaxy.
An artist’s rendering of ESA’s Gaia astrometry spacecraft. Credit: ESA/ATG medialab
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In its observation mode, Gaia spins slowly (once every 6 hours), sweeping its two telescopes across the entire sky and focusing the received light simultaneously onto a single digital camera, the largest flown in space, with nearly a billion pixels (106 CCDs each with 4,500 × 1,996 pixels). It will observe each of its billion stars an average of 70 times over five years. In September 2014, ESA announced that Gaia had discovered its first supernova, Gaia14aaa, some 500 million light-years away from Earth. A minor anomaly, "a stray light problem" was detected shortly after launch that might degrade the quality of some of the results, especially for the faintest stars, but ESA scientists are confident that mitigation schemes will compensate for the problem. In August 2015, Gaia completed its first year of science observations, during which it had recorded 272 billion positional or astrometric measurements, 54.4 billion photometric data points, and 5.4 billion spectra. On 6 November 2015, the spacecraft was placed perfectly to see a lunar transit across the Sun, viewed from Gaia's vantage point as a small, dark circle crossing the face of the Sun. On 14 September 2016, ESA released its first dataset from Gaia that included positions and G magnitudes for about one billion stars based on observations from 25 July 2014 to 16 September 2015. A second data release is planned for April 2018 and will include positions, parallaxes, and proper motions for approximately one billion stars. Final Gaia results in the form of complete datasets are not expected to be publicly available until the early 2020s. Besides its primary goal of mapping stars, Gaia also carries out observations of known asteroids within our solar system, providing data on the orbits and physical properties of these bodies.
241 DESPATCH / ArtSat-2
Nation: Japan (13) Objective(s): heliocentric orbit Spacecraft: DESPATCH / Fuji-Oscar 81 Spacecraft Mass: 30 kg Mission Design and Management: Tama Art University Launch Vehicle: H-IIA (no. F26) Launch Date and Time: 3 December 2014 / 04:22:04 UT Launch Site: Tanegashima / Y1 Scientific Instruments: [none]
Results: DESPATCH (Deep Space Amateur Troubadour's Challenge) or ArtSat-2 was a project developed at Tama Art University to build a 3D-printed sculpture and launch it into deep space. The sculpture, measuring 50 × 50 × 45 centimeters, contained a 7-watt CW radio transmitter that operated in an amateur UHF frequency (437.325 MHz) and transmitted automatically generated "poetic" messages (in English) from space using telemetry numbers derived from voltage and temperature readings on board. As a whole, the project was designed to combine art and technology into a singular whole, to create a "deep-space sculpture" while also producing "generative poetry." The on-board batteries were designed to work for only seven days until the spacecraft was about 3 million kilometers from Earth. After launch and insertion into heliocentric orbit, it separated from the H-IIA upper stage around 06:21 UT on 3 December 2014.
A full-scale prototype (engineering model) of DESPATCH. Credit: ArtSat
<!-- image -->ArtSat personnel received transmissions of its "cosmic poem" after launch, but the poem was transmitted at irregular intervals. By 14 December, ArtSat-2 was already 4.7 million kilometers from Earth and in a 0.7 × 1.3 AU orbit and still transmitting. On 3 January 2015, the Tama Art University team concluded attempts to receive further transmissions from ArtSat-2 since the on-board battery had a lifetime of 27 days after launch. Despite its death, it has fully achieved its goal of being "the most distant artwork in the world." Like its sister spacecraft, Hayabusa-2, PROCYON, and Shin'en 2, DESPATCH performed an Earth flyby on 4 December at a range of 5.8 million kilometers. DESPATCH was also known as Fuji-Oscar 81.
242 DSCOVR
Nation: USA (100) Objective(s): Sun–Earth L1 Lagrange Point Spacecraft: Triana Spacecraft Mass: 570 kg Mission Design and Management: NASA / NOAA / USAF Launch Vehicle: Falcon 9 v1.1 Launch Date and Time: 11 February 2015 / 23:03:02 UT Launch Site: Cape Canaveral / SLC-40
Scientific Instruments:
- PlasMag plasma-magnetometer (magnetometer, Faraday cup, electrostatic analyzer)
- Earth Polychromatic Imaging Camera (EPIC)
- National Institute of Standards and Technology Advanced Radiometer (NISTAR)
Results: Deep Space Climate Observatory (DSCOVR) is a joint mission between NASA, NOAA, and the USAF designed as a successor to NASA's Advanced Composition Explorer (ACE), whose goal is to provide real-time solar wind observations from an L1 orbit. The roots of the project date back to Triana, originally conceived in 1998 by then-Vice President Albert A. Gore, Jr. (1948– ), as a NASA Earth science mission to provide a (near) continuous view of Earth from space (and also use a radiometer to take direct measurements of sunlight reflected and emitted from Earth). Despite being originally slated for launch on STS-107 (the tragic mission of Space Shuttle Columbia in 2003), Triana was canceled in 2001 and the satellite put into storage. Seven years later, in 2008, the Committee on Space Environmental Sensor Mitigation Options (CSESMO) determined that using that spacecraft would be "the optimal solution for meeting NOAA and USAF space weather requirements."
<!-- image -->The satellite was removed from storage in November 2008 and recertified for launch with some modifications. The satellite, designed on the basis of the Small Explorer Program (SMEX-Lite) bus, was launched into an initial orbit of 184 × 186 kilometers at 37° inclination. About 30 minutes following launch, Falcon 9's second stage re-ignited to boost DSCOVR into a 187 × 1,371,156-kilometer transfer orbit at 37° inclination. By 24 February, the spacecraft had reached the halfway mark to the L1 position, traveling nearly 0.8 million kilometers. By 8 June, 100 days after launch, DSCOVR finally reached the Sun–Earth L1 point, and entered a Lissajous orbit, about 1.5 million kilometers from Earth, where it has a continuous view of the Sun and the sunlit side of Earth. Its primary mission is to provide a suite of diverse data on variations in the solar wind, provide early warning on coronal mass ejections, and observe Earth climate changes in ozone, aerosols, dust and volcanic ash, cloud altitudes, and vegetation cover. DSCOVR also takes full Earth pictures about every 2 hours, returning its first views of the entire sunlit side of Earth from approximately 1.6 million kilometers (using the EPIC instrument). In October 2015, NASA launched a Web site that posted at least a dozen new color images every day from EPIC. Earlier, on 16–17 July, the spacecraft took striking images of the Moon moving over the Pacific Ocean near North America. Similar pictures, showing the farside of the Moon had been taken by Deep Impact in May 2008 but from a much further distance of 50 million kilometers. On 28 October 2015, NASA officially handed over control of DSCOVR to NOAA (more specifically, its Space Weather Prediction Center, SWPC) for the latter agency to begin optimizing the final settings for its space weather instruments. The spacecraft completed its first year in deep space on 11 February 2016, now serving as the U.S.'s primary warning system for solar magnetic storms and solar wind data. Real-time data from DSCOVR and space weather forecasts were available to the general public beginning July 2016 from the SWPC Web site; the center also began coordinating the work of DSCOVR with GOES-16 which was launched on 19 November 2016.
243 LISA Pathfinder
Nation: ESA (9) Objective(s): Sun–Earth L1 Lagrange Point Spacecraft: SMART-2 Spacecraft Mass: 1,910 kg Mission Design and Management: ESA Launch Vehicle: Vega (no. VV06) Launch Date and Time: 3 December 2015 / 04:04:00 UT Launch Site: Kourou / ELV
Scientific Instruments:
- LISA Technology Package (LTP)
- Disturbance Reduction System (DRS)
Results: LISA Pathfinder is a technology demonstrator for future spaceborne gravitational wave detectors, such as the proposed Evolved Laser Interferometer Space Antenna (eLISA), tentatively planned for 2034. The spacecraft is equipped to test one of the key concepts behind gravitational wave detectors, that free particles follow geodesics in space-time. It does this by tracking the relative motions of two test masses in nearly perfect gravitational free fall, using picometer resolution laser interferometry. The name "LISA" comes from "Laser Interferometer Space Antenna," an earlier abandoned concept for an observatory to study gravitational waves. The spacecraft has a main science spacecraft and a separable propulsion module, the latter used for raising LISA Pathfinder's orbit after launch and sending it to its operational Lissajous orbit around the Sun–Earth L1 Lagrange Point. The science spacecraft carries two test packages. The first, LTP, contains two identical test masses (Gravitational Reference Sensors), each weighing 2 kilograms in the form of 46-mm gold-platinum cubes suspended in its own vacuum container. Contributors include teams from France, Germany, Italy, the Netherlands, Spain, Switzerland, and the UK. The second, DRS, is a NASA-built system, originally from the canceled Space Technology 7 mission, made up of two clusters of colloidal micro-propulsion thrusters and a computer. LISA Pathfinder was launched into an initial orbit of 208 × 1,165 kilometers. Vega's liquid propellant fourth stage (known as AVUM) then refired to put the spacecraft into a 209 × 1,521-kilometer orbit at 6.0° inclination. The propulsion module then slowly fired six times, thus raising LISA Pathfinder's apogee until it began a cruise to L1. After a six-week trip and a final 64-second firing, the spacecraft arrived in a Lissajous orbit around L1 on 22 January 2016. At 11:30 UT, the propulsion module separated from the science section. Its final orbit was a roughly 500,000 × 800,000-kilometer orbit around L1. About two weeks later, on 3 February, ESA controllers at the European Space Operations Center (ESOC) at Darmstadt, Germany, retracted eight locking "fingers" pressing on the two gold-platinum cubes, at the time held in position by two rods. These rods were retracted from the first test mass on 15 February, and from the second the following day. Finally, on 22 February, controllers set the two cubes completely free to move under the effect of gravity alone, with actively maneuvering spacecraft around them. In the subsequent few months, the LISA Pathfinder team applied a number of different forces to the cubes to study their reaction. For example, one experiment involved raising the temperature of the housing, thus heating the very few gas molecules remaining in there to measure the effect on the cubes. After several months of successful experiments, at 08:00 UT on 25 June 2016, the LTP completed its "nominal operations phase," thus transitioning to work on NASA's DRS experiment.