SECCHI/STEREO at MSSL

SECCHI is a set of remote sensing instruments designed to follow Coronal Mass Ejections (CMEs) from their origins on the Sun, out through the corona and the interplanetary medium and to possible impact with the Earth.

The instrument package comprises 3 telescopes:

EUV Imaging Telescope (EUVI) - a full Sun instrument which images the chromosphere and corona in 4 emision lines: He II 304 A, Fe IX/X 171 A, Fe XII 195 A and Fe XV 284 A.
COR 1 and COR 2 - two white-light coronagraphs to observe the inner (1.1-3 solar radii) and outer (2-15 solar radii) corona at high temporal and spatial resolution, and provide polarization information.
Heliospheric Imager (HI1 and HI2) - these are externally occulted coronagraphs that images the inner heliosphere between the Sun and the Earth between 12-215 solar radii.

STEREO is the first mission dedicated to understanding the physics of CMEs and their effects on the Earth's environment. The mission's overall science objectives are as follows:

Understand the causes and mechanisms of CME inititation
Characterize the propagation of CMEs through the Heliosphere
Discover the mechanisms and sites of energetic particle acceleration in the low corona and the interplanetary medium
Improve determination of the structure of the ambient solar wind

Within these objetives SECCHI has its own primary science goals to:

Determine the 3D structure of coronal loops, coronal streamers and large scale coronal structures
Determine the 3d properties of CMEs
Determine the timing of physical properties involved in CME initiation
Determine the critical forces controlling propagation of CMEs in the corona and interplanetary medium.

The HI instruments, with their unique FOV, will provide the first direct imaging observations of CMEs in the inner heliosphere. As such it will directly address the issue of the forces that control CME evolution and propagation in the corona inner heliopshere, as well as providing insights into the mechanisms and sites of particle acceleration in this region and space weather alerts.

Brief instrument details are given below:

Instrument	PI/Institute	Type	Bandpass	Resolution/FOV
EUVI - EUV Imager	Jim Lemen [Lockheed]	Narrow band Ritchey-Cretien	He II 304, Fe IX 171, Fe XII 195, Fe XV 284 A	1.6 arcsec/pixel 0.9 deg FOV Sun-centred
COR1 - Coronagraph 1	Joe Davila [GSFC]	Internally occulted coronagraph	650-660 nm (brightness and pB)	7.5 arcsec/pixel 1.3-4.0 R (full revolution; Sun centred)
COR2 - Coronagraph 2	Dennis Socker [NRL]	Externally occulted coronagraph	650-750 nm (brightness and pB)	15 arcsec/pixel 2-15 R (full revolution; Sun centred)
HI - Heliospheric Imager	Richard Harrison [RAL]	Externally occulted coronagraph	HI1 - 650-750 nm (brightness)	35 arcsec/pix 20^o circle centred at 13.28^o to Sun centre (3.28-23.28^o along ecliptic)
HI - Heliospheric Imager	Richard Harrison [RAL]	Externally occulted coronagraph	HI2 - 400-1000 nm (brightness)	240 arcsec/pix 70^o circle centred at 53.36^o to Sun centre (18.36-88.36^o along ecliptic)

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