ICESat-2

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ICESat-2
Icesat2 in orbit (cropped).jpg
Artist's impression of ICESat-2 in orbit
Mission typeRemote sensing
OperatorNASA
COSPAR ID2018-070A
SATCAT no.43613
Websiteicesat-2.gsfc.nasa.gov
Mission durationPlanned: 3 years
Elapsed: 2 months, 1 day
Spacecraft properties
BusLEOStar-3[1]
ManufacturerOrbital Sciences/Orbital ATK[1]
Launch mass1,514 kg (3,338 lb)[2]
Payload mass21 kg (46 lb)[3]
DimensionsAt launch: 2.5 × 1.9 × 3.8 m (8.2 × 6.2 × 12.5 ft)[2]
Power1200 W
Start of mission
Launch date15 September 2018, 15:02 (2018-09-15UTC15:02) UTC[4]
RocketDelta II 7420-10C[5][6]
Launch siteVandenberg SLC-2W[6]
ContractorUnited Launch Alliance
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Semi-major axis6,859.05 km (4,262.02 mi)
Eccentricity0.0002983
Perigee478.87 km (297.56 mi)
Apogee482.96 km (300.10 mi)
Inclination92.0027°
Period94.22 minutes
Epoch14 October 2018, 20:29:32 UTC[7]
ICESat-2 logo.png

ICESat-2 (Ice, Cloud, and land Elevation Satellite 2), part of NASA's Earth Observing System, is a satellite mission for measuring ice sheet elevation and sea ice thickness, as well as land topography and vegetation characteristics.[8] ICESat-2, a follow-on to the ICESat mission, was launched on 15 September 2018 from Vandenberg Air Force Base in California,[4] into a near-circular, near-polar orbit with an altitude of approximately 496 km (308 mi). It was designed to operate for three years and carry enough propellant for seven years.[9]

The ICESat-2 mission is designed to provide elevation data needed to determine ice sheet mass balance as well as vegetation canopy information. It will provide topography measurements of cities, lakes and reservoirs, oceans and land surfaces around the globe, in addition to the polar-specific coverage.

The ICESat-2 project is being managed by Goddard Space Flight Center in Greenbelt, Maryland. The sole instrument was designed and built by the center, and the bus was built by and integrated with the instrument by Orbital Sciences (later Orbital ATK).[10] The satellite was launched on a Delta II rocket provided by United Launch Alliance.[11] This was the last launch of the Delta II rocket.

Satellite instruments[edit]

ATLAS instrument integration on ICESat-2

The sole instrument on ICESat-2 is the Advanced Topographic Laser Altimeter System (ATLAS), a space-based lidar. It was designed and built at Goddard Space Flight Center, with the laser generation and detection systems provided by Fibertek.[12][13] ATLAS measures the travel time of laser photons from the satellite to Earth and back; computer programs use the travel time from multiple pulses to determine elevation.[14]

ATLAS emits visible laser pulses at 532 nm wavelength. As ICESat-2 orbits, ATLAS generates six beams arranged in three pairs in order to better determine the surface's slope and provide more ground coverage. Each beam pair is 3.305 km (2.054 mi) apart across the beam track, and each beam in a pair is separated by 2.5 km (1.6 mi) along the beam track. The laser array is rotated 2 degrees from the satellite's ground track so that a beam pair track is separated by about 90 m (300 ft). The laser pulse rate combined with satellite speed results in ATLAS taking an elevation measurement every 70 cm (28 in) along the satellite's ground path.[13][15][16]

The laser fires at a rate of 10 kHz. Each pulse sends out about 200 trillion photons, almost all of which are dispersed or deflected as the pulse travels to Earth's surface and bounces back to the satellite. About a dozen photons from each pulse return to the instrument and are collected with a 79 cm (2.6 ft) beryllium telescope.[3] Beryllium has high specific strength and holds its shape across a large range of temperatures.

The National Snow and Ice Data Center Distributed Active Archive Center manages ICESat-2 science data.[17]

Mission science[edit]

ICESat-2 has four science objectives:[18][19]

  1. Quantify polar ice sheet contributions to current and recent sea-level change and the linkages to climate conditions;
  2. Quantify regional signatures of ice-sheet changes to assess the mechanisms driving those changes and improve predictive ice sheet models; this includes quantifying the regional evolution of ice sheet changes, such as how changes at outlet glacier termini propagate inward;
  3. Estimate sea-ice thickness to examine ice/ocean/atmosphere exchanges of energy, mass and moisture;
  4. Measure vegetation canopy height as a basis for estimating large-scale biomass and biomass change.

In addition, ICESat-2 will take measurements of the height of oceans, inland water bodies like reservoirs and lakes, cities, and ground movements after events like earthquakes or landslides.[18]

Project development[edit]

Launch of ICESat-2

ICESat-2 is a follow-up to the original ICESat mission, which was decommissioned in 2010. When the project entered its first phase in 2010, it was expected to be ready for launch as soon as 2015. In December 2012, NASA reported that they expected the project to launch in 2016. In the following years, technical issues with the mission's only onboard instrument, ATLAS, delayed the mission further, pushing the expected launch back from late 2016 to May 2017.[20] In July 2014, NASA submitted a report to Congress detailing the reasons for the delay and a projected budget overrun, as is required by law for NASA projects which spend at least 15% over budget. In order to finance the budget overrun, NASA diverted funds from other planned satellite missions, such as the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite.[21]

The launch of ICESat-2 took place on 15 September 2018 at 15:02 UTC from Vandenberg Air Force Base Space Launch Complex 2 aboard a Delta II 7420-10C.[4] To maintain a degree of data continuity between the decommissioning of ICESat and the launch of ICESat-2, NASA's airborne Operation IceBridge used a variety of aircraft to collect polar topography and measure ice thickness using suites of laser altimeters, radars, and other systems.[22][23]

Applications[edit]

ICESat-2's Applications program is designed to engage people and organizations who plan to use the data, before the satellite launches. Selected from a pool of applicants, this Science Definition Team represents experts in a wide variety of scientific fields including hydrology, atmospheric science, oceanography, and vegetation science.[24] Early Adopters in the program, including ice scientists, ecologists, and the Navy, work with the ICESat-2 applications team to provide information on how the satellite observations can be used.[25] The goal of this group is to communicate the vast capabilities of the ICESat-2 mission with the greater scientific community, with the aim to diversify and innovate new methods and techniques from the collected data. For example, scientists in the ecology field will be able to use the measurement of vegetation height, biomass, and canopy cover derived from ICESat-2's photon counting lidar (PCL).[26]

See also[edit]

  • CryoSat – European Space Agency (ESA) equivalent to Operation IceBridge and ICESat
  • CryoSat-2 – Follow-on mission to CryoSat

References[edit]

  1. ^ a b Hill, Jeffrey (2 September 2011). "Orbital Sciences Grabs $135 Million NASA ICESat-2 Contract". Via Satellite. Retrieved 23 September 2018.
  2. ^ a b "IceSat-2: Measuring the Height of Earth's Ice from Space" (PDF). NASA. NP-2018-07-231-GSFC. Retrieved 9 September 2018.
  3. ^ a b Ramsayer, Kate (3 November 2014). "NASA Lining up ICESat-2's Laser-catching Telescope". NASA. Retrieved 3 November 2016.
  4. ^ a b c Clark, Stephen (15 September 2018). "Early morning launch closes book on Delta 2 legacy spanning nearly 30 years". Spaceflight Now. Retrieved 16 September 2018.
  5. ^ "Delta 2 to launch ICESat-2". United Launch Alliance. 2018. Retrieved 9 September 2018.
  6. ^ a b Graham, William (14 September 2018). "Delta II concludes amazing legacy with ICESat-2 launch". NASASpaceFlight.com. Retrieved 18 September 2018.
  7. ^ "Object A - Orbit". Heavens-Above. 14 October 2018. Retrieved 14 October 2018.
  8. ^ "ICESAT-2". NASA. Retrieved 14 October 2011.
  9. ^ "ICESat-2" (PDF). Orbital ATK. 2014. Archived from the original (PDF) on 25 October 2016.
  10. ^ Ramsayer, Kate (28 February 2018). "NASA Space Laser Completes 2,000-mile Road Trip". NASA. Retrieved 14 October 2018.
  11. ^ "NASA Selects United Launch Alliance's Workhorse Delta II Rocket for ICESat-2 Mission". United Launch Alliance. 22 February 2013. Retrieved 25 October 2016.
  12. ^ Ramsayer, Kate (3 June 2014). "How NASA Builds a Space Laser". NASA. Retrieved 14 October 2018.
  13. ^ a b "NASA launches 'ICESat-2' laser altimeter". Optics.org. 17 September 2018. Retrieved 14 October 2018.
  14. ^ "ICESat-2: Space lasers". NASA. Retrieved 3 November 2016.
  15. ^ Palm, Steve; Yang, Yeukui; Herzfeld, Ute (16 June 2018). "ICESat-2 Algorithm Theoretical Basis Document for the Atmosphere, Part I: Level 2 and 3 Data Products" (PDF). 7.5. NASA: 8–12.
  16. ^ Neuenschwander, Amy (June 2018). "Ice, Cloud and Land Elevation Satellite (ICESat-2): Algorithm Theoretical Basis Document (ATBD) for Land-Vegetation Along-track Products (ATL08)" (PDF).
  17. ^ "NSIDC: ICESat-2". National Snow and Ice Data Center. Retrieved 3 November 2016.
  18. ^ a b "Science". ICESat-2. NASA. Retrieved 14 October 2018.
  19. ^ "The ICESat-1 Mission: Level-1 Requirements and Mission Success Criteria" (PDF). 4.0. NASA. 8 July 2013. Retrieved 3 November 2016.
  20. ^ Leone, Dan (16 April 2014). "GAO Details Issues with ICESat-2 Sensor". Space News. Retrieved 16 March 2018.
  21. ^ Leone, Dan (1 September 2014). "Paying for IceSat-2 Overruns Delays International Earth Science Launches". Space News. Retrieved 16 March 2018.
  22. ^ Deamer, Kacey (19 May 2017). "NASA's IceBridge Mission Ends Its 'Best Year Ever'". Space.com. Retrieved 5 October 2018.
  23. ^ "IceBridge - Aircraft, Instruments, Satellites". NASA. Retrieved 14 October 2018.
  24. ^ "ICESat-2: Science Definition Team". NASA. 12 July 2017. Retrieved 19 April 2018.
  25. ^ "ICESat-2: Applications". NASA. Retrieved 3 November 2016.
  26. ^ "Lidar Applications for the Study of Ecosystems with Remote Sensing Laboratory". Texas A&M University. Retrieved 19 April 2018.

External links[edit]