SPICE Instrument

The Spectral Imaging of the Coronal Environment (SPICE) instrument is an EUV imaging spectrograph designed to observe both the solar disk and the corona to remotely characterize plasma properties at and near the Sun. Specific scientific topics to be addressed by SPICE include studies of solar wind origin by matching in-situ composition signatures in solar wind streams to surface feature composition, studies of the physical processes that inject material from closed structures into solar wind streams, and studies of SEP source regions by imaging remotely the suprathermal ions thought to be seed populations of SEPs.

The SPICE instrument consists of a single element off-axis parabolic telescope and a toroidal variable line spaced (TVLS) grating spectrograph with two intensified active pixel sensor (IAPS) detectors. SPICE also includes a DPU to control each of the mechanisms, perform data compression and provide the SpaceWire interface to the spacecraft. The off-axis parabola mirror forms an image of the Sun onto the entrance slit assembly containing three interchangeable slits of differing widths. The slit selects a portion of the solar image and passes it to a concave TVLS grating which re-images the spectrally dispersed radiation onto two array detectors. Beyond 0.35 AU, off-limb observations are made by inserting a quartz filter to reduce UV scattered light in the instrument and allow observations of the outer corona beyond >0.30 RS. The two spectral passbands cover the same spatial field of view simultaneously with no scanning of the detectors or grating. The detectors are solar blind, IAPS sensors, and require no visible light rejection filters. The stigmatic spectra produced are magnified, yet maintain high spectral resolution in one dimension and high spatial resolution in the other. The SPICE observing strategy is to produce 2D spectro-heliograms (spectral images) of selected line profiles and line intensities only. The wavelengths covered by SPICE are 702-792 Å (Band 1), 972-1050 Å (Band 2) and 485-525 Å (2nd order). The selected lines represent the full range of temperatures and heights in the solar atmosphere, from the chromosphere to the flaring corona. SPICE derives heritage from Soho/CDS, Soho/SUMER, as well as the RAISE and EUNIS sounding rocket programmes.