The above image was taken at the NASA Infrared Telescope Facility (IRTF) on 12 April 1997 UT with MIRAC2 using a 11.7 micron filter (10% bandwidth). North is up and East to the left, and the image is 44 arcsec on a side. This is a single 6 second integration obtained by observers Casey Lisse & Yan Fernandez (UMD) and Joseph Hora (and telescope operator Bill Golisch) in collaboration with Mike A'Hearn (UMD) and the rest of the MIRAC2 team. The image clearly shows the spiral structure towards the Sun, due to a jet from the comet's surface rotating with the nucleus in an ~11 hour period. The 11.7 um filter contains emission at the peak of the ~300K greybody and silicate emission features from the comet's dust. Hale-Bopp is one of the dustiest comets on record.
MIRAC2 was built and is operated by the University of Arizona and the Smithsonian Astrophysical Observatory. The camera utilizes a Rockwell HF-16 128x128 hybrid Si:As BIB array. MIRAC2 team members are William Hoffmann and Aditya Dayal (UA), Giovanni Fazio and Joseph Hora (SAO), and Lynne Deutsch (BU).
More MIRAC2 Images and profiles of Comet Hale-Bopp at several wavelengths