The sole instrument on ICESat-2 will be the Advanced Topographic Laser Altimeter System (ATLAS). The ATLAS laser will emit visible, green laser pulses at a wavelength of 532 nm.
The laser is developed and built by Fibertek Inc. As ICESat-2 orbits, ATLAS will:
In contrast to the original ICESat design, ICESat-2 will use a micro-pulse, multi-beam approach. This provides dense cross-track sampling to help scientists determine a surface's slope with each pass of the satellite.
The sensor will have a high pulse-repetition rate of 10 kHz (exact number still TBD). This allows the satellite to take measurements every 70 cm along the track.
These instrument features will improve the elevation estimates in sloped areas, as well as rough land surfaces such as crevasses. The ICESat-2 instrument will also improve the ability to estimate the height difference between the polar oceans and sea ice.
Check out how NASA is building the ATLAS lasers: How NASA Builds a Space Laser.