ICESat

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 70 m diameter laser spots that were separated by nearly 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, 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. 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, and at 08:49 UTC on 30 August 2010 it reentered the atmosphere.

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. The satellite was launched on 15 September 2018 aboard a Delta II launch vehicle. 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.

References

References

1. "ICESat (EOS-LAM)". Gunter's Space Page.
2. "Launch Log". Jonathan's Space Report.
3. (17 August 2010). "ICESat Mission Status Report". NASA.
4. (30 August 2010). "Decay Data: ICESat". Space-Track.
5. Clark, Stephen. (25 February 2010). "ICESat mission complete after seven years in orbit". Spaceflight Now.
6. (17 December 2010). "Space laser spies for woodpeckers".
7. "Laser Diode Pump Assembly". NASA.
8. (2005). "Overview of the ICESat Mission". NASA.
9. (27 August 2010). "NASA's Successful Ice Cloud and Land Elevation Mission Comes to an End". NASA.
10. Clark, Stephen. (30 August 2010). "ICESat takes a plunge to conclude successful mission". Spaceflight Now.
11. (26 October 2011). "ICESat-2". NASA.
12. Foust, Jeff. (15 September 2018). "Final Delta 2 launches ICESat-2". SpaceNews.
13. Deamer, Kacey. (19 May 2017). "NASA's IceBridge Mission Ends Its 'Best Year Ever'". Space.com.