JOP141 Emission lines in Near-Sun Comets. Received 15 March 2001 Authors: D.A. Biesecker (LASCO); E. Howell (Arecibo); M. Uzzo, J. Raymond (UVCS) Participants: SOHO/LASCO, SOHO/UVCS, and Arecibo Observatory Objective: To detect emission lines in near-Sun comets, including Kreutz sungrazing comets. Operational considerations: A Target-of-Opportunity JOP to observe near-Sun comets will be conducted beginning in mid-April. Upon notification of a discovery of a near Sun comet with SOHO/LASCO, the SOHO/UVCS instrument and the Arecibo Observatory will make a decision as to whether or not to try to observe the comet as it enters their respective fields of view. This follows the general procedure we have used frequently in the past for LASCO and UVCS alone. See Actions at the end of this description. Nominally, the Arecibo Observatory could observe near-Sun comets from the beginning of April until about mid-September. Arecibo can react to an alert of a comet within 1 hour. In order to observe on a particular day, Arecibo must have positions by 1pm GSFC time. Arecibo: The driver for this campaign is the Arecibo Observatory. The Sun is within the Arecibo FOV above declinations of -2 (minus 2). However, since Kreutz comets approach the Sun from the southern hemisphere, the Sun needs to be well within the FOV in order to observe Kreutz comets. We expect Arecibo to have about a 2 hour window during daylight hours (beginning ~1500 UT) a few days per week for this campaign. We will attempt to observe, at least initially, molecular OH emission lines at 1665 and 1667 MHz and molecular Hydrogen lines around 1216 MHz. The point of contact for Arecibo observations is Ellen Howell (Ph: 787 878 2612 x282; ehowell@naic.edu). If successful, expanding the Arecibo observations to other frequencies will be considered. SOHO/UVCS SOHO/UVCS has observed many near sun comets previously, having observed Ly-alpha emission. The points of contact for SOHO/UVCS are Mike Uzzo (at NASA/GSFC) (Ph: 301 286 3054; uzzo@uvcs6.nascom.nasa.gov) and John Raymond (at CfA) (jraymond@cfa.harvard.edu). UVCS observing restrictions are much less severe than Arecibo. It is expected that if Arecibo commits to observing a near-Sun comet, that UVCS will make every effort to observe as well. The major difference here from earlier studies is that Arecibo may commit to observing fainter comets than UVCS has typically considered as Targets of Opportunity. SOHO/LASCO SOHO/LASCO has the primary responsibility of making the discovery observation, notifying SOHO/UVCS and Arecibo, and ensuring that orbit computations are completed as quickly as possible. The primary point of contact for LASCO is Doug Biesecker (301 286 3116; doug@sungrazer.nascom.nasa.gov) and the secondary contact is Derek Hammer (301 286 3146; derek@sungrazer.nascom.nasa.gov). Actions: When a real-time discovery of a comet is made, the LASCO personnel will make an assessment of the comet brightness and apparent heliocentric distance to determine whether observations by other observatories are feasible. An alert will be sent to Arecibo and SOHO/UVCS, as well as the CBAT, so that they can determine their state of readiness and willingness to observe that particular comet. At the same time, the LASCO personnel will begin processing the LASCO observations in order to send to the CBAT for the reductions and orbit calculations. Contact: Doug Biesecker 301 286 3116 doug@sungrazer.nascom.nasa.gov