RainCube (Radar in a CubeSat) is a technology demonstration mission to enable Ka-band precipitation radar technologies on a low-cost, quick-turnaround platform. Sponsored by NASA’s Earth Science Technology Office (ESTO) through the InVEST-15 program, RainCube developed a 35.75 GHz radar payload to operate within the 6U CubeSat form factor. This mission will validate a new architecture for Ka-band radars and an ultra-compact lightweight deployable Ka-band antenna in a space environment to raise the technology readiness level (TRL) of the radar and antenna from 4 to 7 within the three year life of the program. RainCube will also demonstrate the feasibility of a radar payload on a CubeSat platform. The project completed integration and testing in February 2018 and was delivered in March 2018. RainCube will be delivered to the ISS on the OA-9 resupply mission that launched from NASA’s Wallops Flight Facility in Virginia on May 21.
RainCube has three main objectives:
- Develop, launch, and operate the first radar instrument on a CubeSat (6U)
- Demonstrate new technologies and provide space validation for a Ka-band (35.75 GHz) precipitation profiling radar. At platform altitude of 400 km or less, demonstrate:
- - Radar sensitivity: 20dBZ or better
- - Vertical resolution: 250m
- - Horizontal resolution: 10 km or better
Numerical climate and weather models depend on measurements from space-borne satellites to complete model validation and improvements. Precipitation profiling capabilities are currently limited to a few instruments deployed in Low Earth Orbit (LEO), which cannot provide the temporal resolution necessary to observe the evolution of weather phenomena at the appropriate temporal scale (i.e., minutes). A constellation of precipitation profiling instruments in LEO would provide this essential capability, but the cost and timeframe of typical satellite platforms and instruments make this solution prohibitive. Thus, a new instrument architecture that is compatible with low-cost satellite platforms, such as CubeSats and SmallSats, will enable constellation missions and revolutionize climate science and weather forecasting.
Two key technologies will be validated in the space environment: a miniaturized Ka-band precipitation profiling radar that occupies a 2.5U volume and a 0.5m Ka-band parabolic deployable antenna that stows in a 1.5U volume. Radar instruments have often been regarded as unsuitable for small satellite platforms due to their traditionally large size, weight, and power (SWaP). A novel architecture compatible with the 6U class (or larger) has been developed at JPL, driven by the simplification and miniaturization of the radar subsystems. The RainCube architecture reduces the number of components, power consumption and mass by over one order of magnitude with respect to the existing spaceborne radars. The baseline instrument configuration for the RainCube concept is a fixed nadir-pointing profiler at Ka-band with a minimum detectable reflectivity factor better than +20 dBZ at 250m range resolution. The footprint size (horizontal resolution) is determined by the antenna size. For a nominal orbital altitude of 400 km, the RainCube antenna produces approximately an 8.5 km footprint.
JPL is working with Tyvak Nanosatellite Systems, Inc. in Irvine, CA to fly the RainCube Mission. Tyvak is responsible for developing the spacecraft bus, integrating and testing the flight system, overseeing launch vehicle integration, and managing ground systems and operating the spacecraft once in flight. The spacecraft is based on a tailored version of Tyvak’s Endeavour platform. The Linux based Endeavour avionics board provides a data recorder and processing for the command and data handling and attitude determination & control system. It also interfaces to the inertial reference module, which contains two star cameras, three reactions wheels, and three magnetorquers. RainCube is configured with a 120Whr pack to support high peak charge currents and extended payload operations. Two deployable fixed solar array panels provide up to 45W of peak power. The avionics support active thermal control of the payload and include an imaging system to capture the antenna deployment. Ground communications and data downlink uses a UHF (RX/TX) and S-Band (TX), linked to Tyvak’s mission operations center in Irvine, CA.
NASA ESTO InVEST program
Tyvak Nanosatellite Systems