Laser Operational Periods
The NASA ICESat/GLAS instrument has three lasers, each of which has a 1064 nm laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel for the vertical distribution of clouds and aerosols. The three lasers have been operated one at a time, sequentially throughout the mission. To extend mission life, the operational mode included 33-day to 56-day campaigns, several times per year.
A metadata table, Attributes for ICESat Laser Operations Periods, provided by the ICESat Science Investigator-led Processing System (I-SIPS), was created in an effort to better educate ICESat/GLAS users on the vertical and horizontal accuracies of the data as well as to provide important information on the laser operating periods and data releases. This table is a single source for much of the important data related to these operational campaigns, and it includes:
- Laser transmit energies for the two wavelengths
- Laser footprint size and shape
- Pointing and geolocation accuracies
Click on one of the links below to download the table in the preferred format.
Please see the YXX Release Numbers Web page for information about a new convention for release numbers in file names that was adopted with Release-28.
The ICESat satellite operated in two attitude modes called airplane and sailboat which were named for the orientation of the satellite's solar arrays. Depending on the position of the spacecraft's orbital plane and the sun, the satellite's attitude was changed from airplane to sailboat to accommodate sun angle changes and for power and thermal stability. For more information, see the ICESat Attitudes document (PDF, 120 KB).
Periods and Coverage
ICESat operational periods are summarized in the Table 1 below (courtesy of Christopher A. Shuman, University of Maryland Baltimore County Goddard Earth Sciences and Technology Center, and Vijay P. Suchdeo, Sigma Space at NASA/GSFC).
ICESat World and Polar Elevation Maps 2003-2009
To facilitate visualization of the temporal and spatial coverage of ICESat elevation data, please refer to the World and Polar maps accessible from the View Image links in Table 1 below. These files show elevations from the GLA06 elevation data product at two resolutions, browse and high, although it is not possible to show all the detail in the actual data sets. In addition to these jpg images, there are moderate resolution images provided in Powerpoint format so the images can be seen sequentially. Reduced size sample images are shown below.
Example of ICESat World and Polar Elevation Maps (reduced)
For each elevation map, the lowest elevations, sea level to 500 meters, are shown in dark blue, and the other colors define higher elevations in 500 meter increments. See the scale bars on the maps. All elevations above 4000 meters are represented by a dark red color. Note the relative scale of the polar ice sheets compared to other global, high-elevation land areas; the map projection causes some areal distortion but it is apparent that few other topographic features are as high and wide as the Greenland and Antarctic ice sheets.
White spaces on each of the maps are areas where no elevation data were obtained. This includes gaps along any individual track, generally due to atmospheric losses, as well as between adjacent tracks due to ICESat's 8-day and partial 91-day sampling patterns which both converge at ~86° N and S latitude. In some campaigns the track pattern can be locally distorted, in some cases due to off-nadir pointing of the GLAS laser altimeter. Laser performance variations over the mission life time also impact temporal and spatial coverage of elevation data (see mission calendars). For more information, contact NSIDC User Services.
|Start Date||End Date||Days in Operation||Laser Identifier||World Maps||Polar Maps|
|2003-02-20||2003-03-29||38||1AB||View Image||View Image|
|2003-09-25||2003-11-19||55||2A||View Image||View Image|
|2004-02-17||2004-03-21||34||2B||View Image||View Image|
|2004-05-18||2004-06-21||35||2C||View Image||View Image|
|2004-10-03||2004-11-08||37||3A||View Image||View Image|
|2005-02-17||2005-03-24||36||3B||View Image||View Image|
|2005-05-20||2005-06-23||35||3C||View Image||View Image|
|2005-10-21||2005-11-24||35||3D||View Image||View Image|
|2006-02-22||2006-03-28||34||3E||View Image||View Image|
|2006-05-24||2006-06-26||33||3F||View Image||View Image|
|2006-10-25||2006-11-27||34||3G||View Image||View Image|
|2007-03-12||2007-04-14||34||3H||View Image||View Image|
|2007-10-02||2007-11-05||37||3I||View Image||View Image|
|2008-02-17||2008-03-21||34||3J||View Image||View Image|
|2008-10-04||2008-10-19||16||3K||View Image||View Image|
|2008-11-25||2008-12-17||23||2D||View Image||View Image|
|2009-03-09||2009-04-11||34||2E||View Image||View Image|
|2009-09-30||2009-10-11||12||2F||View Image||View Image|