(U) The Solar Mass Ejection Imager (SMEI) is a proof-of-concept experiment designed to satisfy satisfy requirements of government agencies tasked to forecast space weather. These agencies include the Air Force Space Command, 55th Space Weather Squadron, NOAA's Space Environment Center, and National Space Weather Program. SMEI will predict and improve our understanding of the causes of solar storms.
(U) As our reliance on space systems increases, the importance of predicting and detecting solar activity, mass injections, and geomagnetic disturbances increases. More importantly, over the next several years, solar activity, mass injections, and geomagmetic disturbances will become more frequent. The onset of a geomagnetic storm initiates a wide variety of effects adverse to military and civilian spacecraft and ground-based systems. These include increases in trapped magnetospheric particles, degraded satellite communication and surveillance systems, increased drag and deterioration of attitude control of satellites, and destructive surges in power grids. Advanced warning of such storms would permit preventative measures to alleviate these effects. Large magnetic storms are caused by energetic eruptions from the Sun known as coronal mass ejections (CMEs). The CMEs consist of solar plasma and embedded magnetic fields traveling at up to 1000 km/s (2 million miles/hour). If they pass over the Earth, the fastest and densest of these clouds produce the largest geomagnetic storms. At present, prediction of even large storms is difficult. If CMEs were detected leaving the Sun or along their path to Earth, storm prediction would be greatly enhanced.
(U) SMEI will image mass ejections by detection of sunlight scattered from the free electrons (Thomson scattering) in these denser, hot structures. SMEI will obtain 1 to 3 day forecasts of geomagnetic storms by tracking CMEs from the Sun to near-Earth space. The instrument will image the entire sky in white light once per spacecraft orbit, about every 90 minutes, using baffled camera systems with CCDs.
(U) SMEI will also detect, measure, track and forecast the arrival at Earth of shock waves driven by CMEs and dense structures such as streamers which corotate with the Sun. Development of the SMEI instrument is now underway, with the goal of a launch before the next solar maximum in 2001. Financial support is being provided by NASA, the U.S. Air Force and the University of Birmingham (U.K).
(U) The SMEI is composed of four main subsystems (see photo). Each of the three sensor systems consists of a wide-slit aperture, carefully baffled to minimize stray light, and optics feeding a CCD camera. The baffle/optical systems are rigidly mounted to a spacecraft whose orbital rotation permits a nearly complete survey of the sky once every 90 minutes. It is desireable to place SMEI into an 800-1000 km (450-550 nmiles) circular orbit so that it will be above most of the atmospheric air glow and auroral emission. Each camera covers a different 3 by 60 degree field of view such that, together, they view a thin 180 degree-wide slice of the zenith-facing hemisphere of the sky, sweeping over the entire sky each orbit. A shutter/sensor system protects the detectors from direct solar illumination. After the contribution of stars is removed, the instrument's basic product will be a 90-minute cadence of all-sky maps of heliospheric brightness flux. These maps will have an angular resolution of about 1 degree and a photometric precision equivalent to the brightness of a 12th magnitude star.
(U) To be supplied.
|SMEI||Solar Mass Ejection Imager|
|SWATH ACTD||Space Weather and Terrestrial Hazards (SWATH) ACTD|
|Space-Based Sensors||Space Based Sensors|
|ENVIRONMENTAL MONITORING||SPACE FORCE ENHANCEMENT: ENVIRONMENTAL MONITORING|
|SMEI Experiment Homepage|
(U) DoD: OASD(C3I), Pentagon, Washington, DC
(U) Service Staff: SAF/AQS, Pentagon, Washington, DC
(U) Major Command: HQ AFSPC/DR, Peterson AFB, CO
(U) Program Management: HQ AFMC/SMC, Los Angeles AFB, CA
(U) National Security Space Road Map Team, NSSA, Open Phone: (703) 808-6040, DSN 898-6040.
(U) 27 October 1997
(U) Road Map Production Date: 23 June 2001