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HeDI (Helium Doppler Imager) is a 3U CubeSat mission developed by NASA's Goddard Space Flight Center designed to provide spatially resolved Doppler shifts during the impulsive phase of solar flares.

HeDI is developed by the Goddard Space Flight Center, and the platform is built by the University of Arizona. The main objective is the feasibility demonstration for a full scale payload. The instrument will use only readily available components. The Institut d’Astrophysique Spatiale and the Institut d’Optique will provide the EUV multilayer optics, based on the developments ongoing for the Solar Orbiter mission.

By monitoring the entire solar disk for Doppler shifts in He II 304 Å over a period of months, HeDI will observe multiple C and M class flares, with a significant probability of observing larger flares as well. HeDI will provide a measure of the He II 304 Å Doppler shift with a sensitivity to shifts of 30 km/s and greater, resolved on a spatial scale of 10 arcsec – the typical scale of active region features such as loop foot points where coronal heating and electron beams can result in fast upflows of evaporated chromospheric material. Since HeDI is designed to monitor the solar disk on every orbit during the mission lifetime (90 days target, 30 days minimum) with a cadence of 5 s (25 ms integration), He II Doppler shifts would be observed to provide unique constraints on energy deposition during the flare impulsive phase.

It was selected in 2011 by NASA to be launched as part of the ELaNa program.

Nation: USA
Type / Application: Astronomy, solar
Operator: NASA Goddard Space Flight Center, SwRI
Contractors: NASA Goddard Space Flight Center
Equipment: HeDI
Configuration: CubeSat (3U)
Propulsion: None
Power: Solar cells, batteries
Lifetime: 90 days
Mass: 4 kg ?
Satellite COSPAR Date LS Launch Vehicle Remarks
HeDI - with ?