ICESat

{{short description|NASA satellite to observe ice sheets, clouds, and land (2003–2010)}}

{{Infobox spaceflight

| name = ICESat-1

| names_list = Ice, Cloud, and land Elevation Satellite

| image = icesat.jpg

| image_caption = Artist's rendering of the ICESat-1 satellite

| image_size = 300px

| mission_type = Earth observation

| operator = NASA

| COSPAR_ID = 2003-002A

| SATCAT = 27642

| website = [https://icesat.gsfc.nasa.gov/ ICESat]

| mission_duration = 5 years (planned)
{{time interval|13 January 2003 00:45|February 2010|show=ym|sep=,}} (achieved)

| spacecraft_bus = BCP-2000

| manufacturer = Ball Aerospace{{cite web|url=http://space.skyrocket.de/doc_sdat/icesat.htm|title=ICESat (EOS-LAM)|publisher=Gunter's Space Page|access-date=31 August 2010}}

| launch_mass = {{cvt|970|kg}}

| dimensions = {{cvt|2|xx|2|xx|3.1|m}}

| power = 640 watts

| launch_date = 13 January 2003, 00:45:00 UTC{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|publisher=Jonathan's Space Report|access-date=31 August 2010}}

| launch_rocket = Delta II 7320-10
D-294

| launch_site = Vandenberg, SLC-2W

| launch_contractor = Boeing

| entered_service = 2003

| declared = October 11 2009{{cite web|url=https://icesat.gsfc.nasa.gov/icesat/|title=ICESat Mission Status Report|publisher=NASA|date=17 August 2010|archive-url=https://web.archive.org/web/20180916221820/https://icesat.gsfc.nasa.gov/icesat/|archive-date=16 September 2018}} {{PD-notice}}

| deactivated = 14 August 2010, 17:37 UTC

| decay_date = 30 August 2010, 08:49 UTC {{cite web|url=https://www.space-track.org/basicspacedata/query/class/tip/NORAD_CAT_ID/27642/orderby/ID%20DESC/format/html/|title=Decay Data: ICESat|publisher=Space-Track|date=30 August 2010|access-date=18 September 2018}}

| orbit_reference = Geocentric orbit

| orbit_regime = Low Earth orbit

| orbit_periapsis = {{cvt|586|km}}

| orbit_apoapsis = {{cvt|594|km}}

| orbit_inclination = 94.00°

| orbit_period = 96.60 minutes

| apsis = gee

| insignia = ICESat logo.png

| insignia_caption = ICESat mission patch

| insignia_size = 200px

| programme = Large Strategic Science Missions
Earth Science Division

| previous_mission = Aqua

| next_mission = Aura

| programme2 = Earth Observing System

| previous_mission2 = Aqua

| next_mission2 = SORCE

}}

ICESat (Ice, Cloud, and land Elevation Satellite) was a NASA satellite mission for measuring ice sheet mass balance, cloud and aerosol heights, as well as land topography and vegetation characteristics. It operated as part of NASA's Earth Observing System (EOS). ICESat was launched 13 January 2003 on a Delta II launch vehicle from Vandenberg Air Force Base in California into a near-circular, near-polar orbit with an altitude of approximately {{cvt|600|km}}. It operated for seven years before being retired in February 2010, after its scientific payload shut down and scientists were unable to restart it.{{cite web|url=http://www.spaceflightnow.com/news/n1002/25icesat/|title=ICESat mission complete after seven years in orbit|date=25 February 2010 |publisher=Spaceflight Now|first=Stephen|last=Clark|access-date=25 February 2010}}

The ICESat mission was designed to provide elevation data needed to determine ice sheet mass balance as well as cloud property information, especially for stratospheric clouds common over polar areas. It provides topography and vegetation data around the globe, in addition to the polar-specific coverage over the Greenland and Antarctic ice sheets. The satellite was found useful in assessing important forest characteristics, including tree density.{{cite news|url=https://www.bbc.co.uk/news/science-environment-11867165|title=Space laser spies for woodpeckers|agency=BBC News|date=17 December 2010}}

Satellite instruments

The sole instrument on ICESat was the Geoscience Laser Altimeter System (GLAS), a space-based lidar. GLAS combined a precision surface lidar with a sensitive dual-wavelength cloud and aerosol lidar. The GLAS lasers emit infrared and visible laser pulses at 1064- and 532-nm wavelengths. As ICESat orbited, GLAS produced a series of approximately {{cvt|70|m}} diameter laser spots that were separated by nearly {{cvt|170|m}} along the spacecraft's ground track. During the commissioning phase of the mission, the ICESat was placed into an orbit which allowed the ground track to repeat every 8 days. During August and September 2004, the satellite was maneuvered into a 91-day repeating ground track for the main portion of the mission.

Operational history

ICESat was designed to operate for three to five years. Testing indicated that each GLAS laser should last for two years, requiring GLAS to carry three lasers in order to fulfill the nominal mission length. During the initial on orbit test operation, a pump diode module on the first GLAS laser failed prematurely on 29 March 2003. A subsequent investigation indicated that a corrosive degradation of the pump diodes, due to an unexpected but known reaction between indium solder and gold bonding wires,{{cite web|url=http://nepp.nasa.gov/wirebond/laser_diode_arrays.htm|archive-url=https://web.archive.org/web/20040314033521/http://nepp.nasa.gov/wirebond/laser_diode_arrays.htm|url-status=dead|archive-date=14 March 2004|title=Laser Diode Pump Assembly|publisher=NASA}} {{PD-notice}} had possibly reduced the reliability of the lasers. Consequentially, the total operational life for the GLAS instrument was expected to be as little as less than a year as a result. After the two months of full operation in the fall of 2003, the operational plan for GLAS was changed, and it was operated for one-month periods out of every three to six months in order to extend the time series of measurements, particularly for the ice sheets.{{cite journal|last1=Schutz|first1=B. E.|first2=H. J.|last2=Zwally|first3=C. A.|last3=Shuman|first4=D.|last4=Hancock|first5=J. P.|last5=DiMarzio|year=2005|title=Overview of the ICESat Mission|journal=Geophysical Research Letters|publisher=NASA|volume=32|issue=21|page=L21S01|doi=10.1029/2005GL024009|url=http://icesat.gsfc.nasa.gov/icesat/publications/GRL/schutz-1.pdf|bibcode=2005GeoRL..3221S01S|hdl=11603/24281 |s2cid=129436274 }} {{PD-notice}} The last laser failed on 11 October 2009, and following attempts to restart it, the satellite was retired in February 2010. Between 23 June 2010 and 14 July 2010, the spacecraft was maneuvered into a lower orbit in order to speed up orbital decay. On 14 August 2010, it was decommissioned,{{cite web|url=http://www.nasa.gov/mission_pages/icesat/icesat-end.html|title=NASA's Successful Ice Cloud and Land Elevation Mission Comes to an End|date=27 August 2010|publisher=NASA|access-date=31 August 2010|archive-date=29 August 2010|archive-url=https://web.archive.org/web/20100829195935/http://www.nasa.gov/mission_pages/icesat/icesat-end.html|url-status=dead}} {{PD-notice}} and at 08:49 UTC on 30 August 2010 it reentered the atmosphere.{{cite web|url=http://www.spaceflightnow.com/news/n1008/30icesat/|title=ICESat takes a plunge to conclude successful mission|last=Clark|first=Stephen |date=30 August 2010|publisher=Spaceflight Now|access-date=31 August 2010}}

Follow-on satellite

A follow-on mission, ICESat-2, was developed by NASA to continue studying polar ice changes, and the biomass and carbon in vegetation.{{cite web|title=ICESat-2|url=http://icesat.gsfc.nasa.gov/icesat2/ |publisher=NASA|date=26 October 2011|access-date=5 November 2011}} The satellite was launched on 15 September 2018 aboard a Delta II launch vehicle.{{cite news |url=https://spacenews.com/final-delta-2-launches-icesat-2/|title=Final Delta 2 launches ICESat-2|publisher=SpaceNews|first=Jeff|last=Foust|date=15 September 2018|access-date=5 October 2018}} For the period of time in between the two satellites, NASA's Operation IceBridge used a Douglas DC-8 aircraft as a stopgap to measure ice thickness and collect other data.{{cite news |url=https://www.space.com/36920-nasa-2017-icebridge-mission-ends.html|title=NASA's IceBridge Mission Ends Its 'Best Year Ever'|publisher=Space.com|first=Kacey|last=Deamer|date=19 May 2017|access-date=5 October 2018}}

References

External links

[https://icesat.gsfc.nasa.gov/icesat/ ICESAT] by NASA's Goddard Space Flight Center
[http://www.csr.utexas.edu/glas/ ICESAT/GLAS] {{Webarchive|url=https://web.archive.org/web/20220808150907/http://www.csr.utexas.edu/glas/ |date=8 August 2022 }} by the Center for Space Research, University of Texas