DAVID F. WEBB's PROJECTS


Solar Mass Ejection Imager (SMEI)

coriolis patch
The Solar Mass Ejection Imager (SMEI) is an all-sky camera experiment capable of imaging coronal mass ejections (CMEs) as they propagate from the Sun through the solar wind or inner heliosphere. Successful operation of the SMEI will significantly improve space weather forecasting. Detection of potentially damaging Earth-bound CMEs will help to protect space assets and maintain stable communications, capabilities important to both the military and civilians. SMEI’s all-sky images may also help astrophysicists in understanding solar processes and detecting astronomical phenomena. SMEI is part of the Space Test Program's Coriolis Mission which was launched into an 840 km circular, sun-synchronous orbit on 6 January 2003.  

A main goal of SMEI is to obtain 1-3 day forecasts of magnetic storms at Earth by tracking CMEs from the Sun to near-Earth space. SMEI has already accomplished this major milestone by observing its first Earth-directed ("halo") CME in late May 2003. This fast (1000 km/s) event was detected in the all-sky SMEI images ~15 hours before it passed over the Earth on May 29-30 causing a major geomagnetic storm. The CME erupted from the Sun following two X-class flares from an active region near Sun center. The two ejections likely merged to become a single halo, which was seen moving outward near the Sun by the SoHO/LASCO coronagraphs.  Since launch, SMEI has also observed several dozen CMEs viewed in projection coming off the solar limb heading out into space.

I have been working with SMEI team members since the mid-1980s on advocating and developing the concept. I wrote the original proposal sent to NASA and helped with the many SMEI briefings by Air Force personnel and others. I helped analyze the background readiation environment for various SMEI orbits, and am a liason for other researchers and spacecraft experiments with which SMEI might be complementary. Some details of the experiment can be found here.  A cadcam drawing of the SMEI instrument is shown below, and a photo of one of the flight units below that. Each of the three triangular baffles, shown with their outer doors opened, are mounted to a strongbox containing the optics and CCD cameras. These in turn are connected to the main electronics box. The vertical plates cool the CCDs by radiating heat to deep space. 

SMEI Instrument illustration

Next is a photo of one of the actual flight baffles attached to the strongbox with a flat cold plate. This was during recent vibration testing at the University of Birmingham, UK.

flight baffle



When indivdual frames from each camera are stitched together and mapped into ecliptic coordinates, a complete sky map can be built up over an orbit, except for small areas centered on the Sun and in the anti-Solar direction. One such map, an equal-area Hammer-Aitoff projection, produced in March 2003 is shown below. It is centered on the Sun with the North and  South ecliptic poles at the top and bottom, resp. The dark circle is a zone of exclusion 20 deg. in radius centered on the Sun. Some features of interest include the Zodiacal light on either side of the disk, Venus to the right, the Milky Way, Orion to the left, and the Magellanic Clouds at the bottom.

smei composite


One of the brightest of the limb CMEs seen by SMEI is shown in the panels below.  It erupted from the Sun on May 31, 2003 with a high speed of nearly 2000 km/sec.  The + sign marks the location of  the Sun within the exclusion zone; the CME loop is imaged by SMEI when it is about 30 deg. elongation from the Sun.

May 2003 CME



The SECCHI Experiment on the STEREO Mission

I am a Co-Investigator on the SECCHI experiment that is being developed for launch on the twin STEREO missions in 2005 (hopefully).  SECCHI is a suite of remote sensing instruments consisting of two white light coronagraphs (COR1 and COR2) and an EUV imager (EUVI), collectively referred to as the Sun Centered Imaging Package (SCIP), and a two Heliospheric Imagers (HI). SECCHI will follow in three-dimensions Coronal Mass Ejections (CMEs) from their origin at the Sun, through the corona and interplanetary medium, to impact at Earth. We anticipate major breakthroughs in understanding the origin and consequences of CMEs, in determining their three-dimensional structure, in identifying the magnetic configurations and evolutionary paths leading to CMEs, in determining the key factors controlling their trajectories, and in achieving the national goal of predicting space weather. Details about SECCHI can be found  here. Here is a view of the SECCHI instrument. The COR 1 and COR2 instruments are on the bottom and the EUVI is on the top.

SECCHI Instrument


 

And here is a mockup of the HI instrument, which actually consists of two subsystems, one for viewing the sky near the Sun and the other out to beyond the Earth.  Details can be found at the HI PI's home site in England. 

HI Instrument


I am also a Co-I on the HI experiments and, as a SMEI team member, act as liason between SMEI and SECCHI.  And I am the Space Weather Coordinator for SECCHI and, mostly by default, for the rest of STEREO. More details on that can be found on our STEREO Space Weather site.  


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