D. Judge, A. Jones, D. McMullin, P. Gangopadlhyay
Space Science Center
University of Southern California
Los Angeles, CA 90089
1 June 1999
The Solar EUV Monitor (SEM) is a small transmission grating spectrometer that continuously measures the full disk absolute solar flux in the He II (30.4 nm) line as well as the absolute flux between 1 and 50 nm. The SEM has flown successfully on both sounding rockets and SoHO.
On STEREO SEM could provide important ancillary data to other instruments, as well as provide an established space weather beacon instrument.
SEM would allow the calibration of the EUV imagers on STEREO by providing calibrated absolute fluxes, in the same way it is used by EIT on SoHO. SEM can also follow impulsive and gradual solar events, associated with flares and CMEs respectively, with high temporal resolution. In conjunction with the imagers SEM data would help to identify CME precursors. As a space weather beacon observing the EUV photon flux the SEM could provide a 20 hour advance warning of incoming energetic particles, and with the stereo view false alerts of non Earth-directed events could be excluded. The low data rate of 5bps is also highly compatible with a space weather beacon.
The mass (~ 500g) power (~ 500mW) and bandwidth (~5bps) requirements for SEM are very modest.