ICESat-2

ICESat-2
Artist's impression of ICESat-2 in orbit
Mission type Remote sensing
Operator NASA
COSPAR ID 2018-070A
SATCAT no. 43613
Website icesat-2.gsfc.nasa.gov
Mission duration Planned: 3 years
Elapsed: 1 month, 3 days
Spacecraft properties
Bus LEOStar-3[1]
Manufacturer Orbital Sciences[1]
Launch mass 1,514 kg (3,338 lb)[2]
Dimensions At launch: 2.5 × 1.9 × 3.8 m (8.2 × 6.2 × 12.5 ft)[2]
Power 1200 W
Start of mission
Launch date 15 September 2018, 15:02 (2018-09-15UTC15:02) UTC[3]
Rocket Delta II 7420-10C[4][5]
Launch site Vandenberg SLC-2W[5]
Contractor United Launch Alliance
Orbital parameters
Reference system Geocentric
Regime Low Earth
Semi-major axis 6,839.99 km (4,250.17 mi)
Eccentricity 0.0003924
Perigee 459.17 km (285.32 mi)
Apogee 464.54 km (288.65 mi)
Inclination 92.0068°
Period 93.83 minutes
Epoch 18 September 2018, 03:03:45 UTC[6]

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.[7] ICESat-2, a follow-on to the ICESat mission, was launched on 15 September 2018 from Vandenberg Air Force Base in California,[3] 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.[8]

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 provided by Orbital ATK. The satellite was launched on a Delta II rocket provided by United Launch Alliance.[9] This was the last launch of the Delta ll launch vehicle.

Satellite instruments

The sole instrument on ICESat-2 is the Advanced Topographic Laser Altimeter System (ATLAS), a space-based LIDAR. 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.[10]

ATLAS instrument integration on ICESat-2

The ATLAS laser emits visible laser pulses at 532 nm wavelength. The laser was developed and built by Fibertek. As ICESat-2 orbits, the ATLAS generates six beams arranged in three pairs, with the pairs 3.3 km apart, in order to better determine the surface's slope and provide more ground coverage. ATLAS takes elevation measurements every 70 cm along the satellite's ground path.

The laser fires at a rate of 10 kHz. Each pulse sends out about 20 trillion photons, almost all of which are dispersed or deflected as the pulse travels to Earth's surface and bounces back to the satellite.[11] About a dozen photons from each pulse return to the instrument and are collected with a beryllium telescope. 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.[12]

Mission science

ICESat-2 has four science objectives:

  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.[13]

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.

NASA's airborne mission Operation IceBridge is collecting data to bridge the gap between ICESat and ICESat-2.

Project development

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.[14] 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 has diverted funds from other planned satellite missions, such as the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite.[15] The launch took place on 15 September 2018 at 15:02 UTC from Vandenberg Air Force Base Space Launch Complex 2 aboard a Delta 2 7420-10C.[3] To maintain data continuity in the interim between the decommissioning of ICESat and the launch of ICESat-2, NASA's airborne Operation IceBridge mission has continued to collect polar topography data using its onboard ATM lidar sensor.[16]

Applications

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.[17] 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.[18] 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).[19]

See also

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

References

  1. 1 2 "ICESAT-2 (OSC)". Orbital Sciences. Archived from the original on 26 October 2011. Retrieved 14 October 2011.
  2. 1 2 "IceSat-2: Measuring the Height of Earth's Ice from Space" (PDF). NASA. NP-2018-07-231-GSFC. Retrieved 9 September 2018.
  3. 1 2 3 Clark, Stephen (15 September 2018). "Early morning launch closes book on Delta 2 legacy spanning nearly 30 years". Spaceflight Now. Retrieved 16 September 2018.
  4. ↑ "Delta 2 to launch ICESat-2". United Launch Alliance. 2018. Retrieved 9 September 2018.
  5. 1 2 Graham, William (14 September 2018). "Delta II concludes amazing legacy with ICESat-2 launch". NASASpaceFlight.com. Retrieved 18 September 2018.
  6. ↑ "Object A - Orbit". Heavens-Above. 18 September 2018. Retrieved 18 September 2018.
  7. ↑ "ICESAT-2". NASA. Retrieved 14 October 2011.
  8. ↑ "ICESat-2" (PDF). Orbital ATK. 2014. Archived from the original (PDF) on 25 October 2016.
  9. ↑ "NASA Selects United Launch Alliance's Workhorse Delta II Rocket for ICESat-2 Mission". United Launch Alliance. 22 February 2013. Retrieved 25 October 2016.
  10. ↑ "ICESat-2: Space lasers". NASA. Retrieved 3 November 2016.
  11. ↑ Ramsayer, Kate (3 November 2014). "NASA Lining up ICESat-2's Laser-catching Telescope". NASA. Retrieved 3 November 2016.
  12. ↑ "NSIDC: ICESat-2". National Snow & Ice Data Center. Retrieved 3 November 2016.
  13. ↑ "The IceSat-2 Mission: Level-1 Requirements and Mission Success Criteria" (PDF). NASA. 8 July 2013. Retrieved 3 November 2016.
  14. ↑ Leone, Dan (16 April 2014). "GAO Details Issues with ICESat-2 Sensor". Space News. Retrieved 16 March 2018.
  15. ↑ Leone, Dan (1 September 2014). "Paying for IceSat-2 Overruns Delays International Earth Science Launches". Space News. Retrieved 16 March 2018.
  16. ↑ "ICESat-2". eoPortal. European Space Agency. Retrieved 16 March 2018.
  17. ↑ "ICESat-2: Science Definition Team". NASA. 12 July 2017. Retrieved 19 April 2018.
  18. ↑ "ICESat-2: Applications". NASA. Retrieved 3 November 2016.
  19. ↑ "Lidar Applications for the Study of Ecosystems with Remote Sensing Laboratory". Texas A&M University. Retrieved 19 April 2018.
  • ICESat-2 by NASA's Goddard Space Flight Center
  • ICESat/GLAS by the Center for Space Research, University of Texas
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