Key ICESat-2/ATLAS Performance Specifications
|Nominal duration of mission||3 Years|
|Number of beams||6 organized in 3 pairs|
|Footprint size||17 m|
|Field of view||45 m|
|Pulse repetition frequency||10kHz (~0.7m on the ground)|
|Laser wavelength||532 nm|
|Pointing control||45 m|
|Pointing knowledge||6.5 m|
|Single-photon time-of-flight precision||800 ps|
ATLAS expected performance in range using the current best estimates for winter and
Lambertian surface reflectance
N signal photons per shot
N signal photons per shot
|100-shot std dev (weak beam)||100-shot std dev (strong beam)|
|Ice sheet (interior)||0.9 -0.98||0.4 - 3.0||1.6 - 12.0||4 - 9||2 - 4|
|Ice sheet (glaciers)||0.6 - 0.9||0.6 - 1.0||0.6 - 3.9||12 - 29||6 - 14|
|Sea Ice||0.8 - 0.9||0.6 - 2.1||2.3 - 8.5||5 - 8||3 - 4|
* - 0.2
(much higher when specular)
|0.05 - 0.2||0.2 - 1.0||2 - 5||2 - 5|
Orbit and coverage
(coverage up to 88 degrees north and south)
|Semi-major axis||6855 km|
91-day exact repeat orbit
Links to the kmz file for the polar regions of all the lasers tracks over a 91-day period.
Kmz File for other areas upcoming or on request.
RGTs with Dates and Times (UTC) Cycle #01
RGTs with Dates and Times (UTC) Cycle #02
RGTs with Dates and Times (UTC) Cycle #03
Western Hemisphere Ground Tracks
Eastern Hemisphere Ground Tracks
These are posted at a fairly low resolution in order to make the file size manageable, with one point approximately every 7 kilometers.
The files have seven tracks per orbit: one for each of the six beams of ICESat-2, and the seventh for the Reference Ground Track (RGT). The RGT is an imaginary line through the six-beam pattern that is handy for getting a sense of where the orbits fall on Earth, and which the mission uses to point the observatory. However, the six tracks for the six beams are our best estimate of where the beams will actually fall on Earth’s surface.
As of 13 October 2018, we have entered our mission orbit and are pointing at the RGT! Updated KML files have been posted to this website containing individual files for each RGT with a date and time stamp posted every 420 kilometers along-track (roughly 1 minute of flight time in between each point). Our first RGT is #234; this is where the time series begins. The date of each RGT is in the file name, so the user can easily ascertain where ICESat-2 will be on a particular day.
Over the polar areas and oceans, ICESat-2 will repeat its ground tracks every 91 days as it orbits; over land the satellite will point slightly off the RGT to measure more of Earth’s forests. The transitions between repeat-track pointing and off-pointing are included in these ground tracks. Near the poles, the difference between the two is subtle, but it becomes more pronounced near the equator.
The order of the off-point sequence has not yet been determined. During the first 91-day period, the satellite will point at the RGT, and after that it will follow one of seven off-pointing plans. The different sets of 91-day plans are included in the kmz files.
The ground tracks will likely change slightly as ICESat-2 nears launch and conducts post-launch calibration maneuvers. The mission is exploring options to provide more up-to-date pointing plans to the community as we approach the data-collection stage.
- Remember that while these represent the nominal location of the sub-satellite point with associated date/time of the ICESat-2 overpass, the pointing control (~45 meters) and pointing knowledge are still not up to missions specifications so any calibration/validation activities that are planned in conjunction with these ICESat-2 RGTs should take that into consideration while the POD/PPD teams continue to work on improving pointing.