The 2003 Mercury Transit
The 3 CDS wide-slit images above (from 3 different observation
sequences) are contrast-enhanced
Caption: Yes, we have images and movies of the 2003 Mercury transit as seen from the SOHO spacecraft! Since SOHO in its halo orbit was a bit "ahead" of Earth at the time, Mercury's shadow caught up with SOHO a little later than with observers on Earth. The transit itself started at 7:48 UT and ended at 13:16 UT; Mercury was, however, visible in EIT images against the extended corona for some hours before and after. Although our webserver was crumbling under the huge number of requests, the event was not just good PR - three instruments made a series of special observations:
MDI took a series of full disk continuum images at varying focus positions during the entire transit, in order to better determine absolute spacecraft roll and MDI absolute plate scale, and to better understand MDI image distortion. The varying focus positions are what causes the Sun to "breathe", or "pulsate" in size, in the movie.
CDS took a wide variety of observations (wide slit movies, narrow slit rasters, and narrow slit sit-and-stare sequences). One of the aims is to better characterize the three-dimensional (wavelength, X and Y) point spread function of the optics.
EIT took series of images in all four wavelengths, to improve models of stray light and their flatfielding.
We're happy to say that although our server was not keeping up with the request during the event, the data processing pipelines (including telemetry downlink) worked flawlessly through the event, with no significant data loss.
Links to [near] real time images from other observatories:
Credits: SOHO/EIT, SOHO/MDI (ESA & NASA)
Special thanks to: Bud Benefield, Bob Dutilly, Sarah Gregory, Joe Gurman, Steele Hill, Scott McIntosh, Craig Roberts, Julia Saba, Kevin Schenk