Enabling Global Observations of Clouds and Precipitation at Fine Spatiotemporal Scales from 6U-Class SmallSat Constellations: Temporal Experiment for Storms and Tropical Systems Technology Demonstration (TEMPEST-D)

The Temporal Experiment for Storms and Tropical Systems (TEMPEST) mission concept consists of a constellation of 5 identical 6U-Class satellites observing storms at 5 millimeter-wave frequencies with 5-10 minute temporal sampling to observe the time evolution of clouds and their transition to precipitation. Such a small satellite mission would enable the first global measurements of clouds and precipitation on the time scale of tens of minutes and the corresponding spatial scale of a few km. TEMPEST is designed to improve the understanding of cloud processes by providing critical information on temporal signatures of precipitation and helping to constrain one of the largest sources of uncertainty in cloud models. TEMPEST millimeter-wave radiometers are able to perform remote observations of the interior of the cloud to observe microphysical changes as the cloud begins to precipitate or ice accumulates inside the storm.

The TEMPEST technology demonstration (TEMPEST-D) mission is in development to raise the TRL of the instrument and spacecraft systems from 6 to 9 as well as to demonstrate radiometer measurement and differential drag capabilities required to deploy a constellation of 6U-Class satellites in a single orbital plane. The TEMPEST-D millimeter-wave radiometer instrument provides observations at five frequencies from 89 to 183 GHz using a single compact instrument designed for 6U-Class satellites. The direct-detection topology of the radiometer receiver substantially reduces its power consumption and eliminates the need for a local oscillator and mixer, thereby decreasing complexity compared to heterodyne receivers. The TEMPEST-D instrument is self-calibrating, using a cross-track scanning reflector to view an ambient blackbody calibration target and cosmic microwave background every scan period, enabling precision end-to-end calibration of the millimeter-wave radiometers. The TEMPEST-D radiometer instrument has been fabricated and successfully tested under environmental conditions (vibration, thermal cycling and vacuum) expected in low-Earth orbit.

The top-level requirements for the TEMPEST-D mission are to: (1) demonstrate precision inter-satellite calibration between TEMPEST-D and one other orbiting radiometer (e.g. GPM or MHS) measuring at similar frequencies; and (2) demonstrate orbital drag maneuvers to control altitude to 100 m or better, as verified by GPS, sufficient to achieve required temporal spacing in a constellation of 6U-Class satellites.

TEMPEST-D began in August 2015, with a rapid 2.5-year development to deliver a complete flight system with integrated payload by February 2018. TEMPEST-D has been manifested by NASA CSLI and is planned for launch on ELaNa-23, a commercial resupply service to the ISS on a Cygnus Antares II, in March 2018. The TEMPEST-D satellite is expected to be deployed into a 400-km orbit at 51.6° inclination several months after arriving at the ISS.