The objective of the STSP in 2004-2005 is to provide scientifically useful observations of Tempel 1 to complement data taken at large telescopes. In particular, the program will focus on the continuous monitoring of the comet before, during, and after impact for:
Time on large telescopes is very limited, resulting in temporal gaps in the data for Tempel 1. However, observers with small telescopes often have discretionary observing time and can thus monitor the comet for several days, weeks, and months to help fill the gaps in the data taken at large telescopes. Also, small telescopes equipped with CCDs are often fast systems with wide fields of view and broadband filters. This combination is good for performing the types of observations noted above.
Changes in the brightness of the dust coma. As the comet orbits the Sun, the rate of dust production changes, with an asymetric peak occuring about 90 days before perihelion. During the peak, dust production can be over 10 times greater than the months before and after perihelion. During the 2000 observing campaign, STSP observers contributed valuable R-band images from which we extracted photometric measurements of the dust coma and calculated dust production rates (see Ref. 1). These results helped to fill in the dust lightcurve from about 60 to 355 days after perihelion. A preliminary plot of this lightcurve, which is a baseline of dust activity, is available here. STSP observations from November 2004, through impact on July 4, 2005, will help fill in the pre-perihelion section of this baseline (perihelion occurs on July 5, 2005). The impact may affect dust production. Therefore, observations made after impact and through December 2005 will be compared to the pre-impact baseline. Differences may help us refine our knowledge of the nucleus and interior of Tempel 1.
It is important to note that broadband-RI imaging and photometry are used for cometary dust studies because dust preferentially scatters red light. The broadband-R filter captures the flux of sunlight scattered by dust within the wavelength range of 550-850 nanometers while the broadband-I filter captures dust flux within 700-1000+ nanometers. Also, gas emissions from the coma are minimal in the RI bands; nearly all of the flux is due to dust.
Features in the coma and tail. Cometary gas and dust activity can manifest itself as jets and fans in the coma. The dust tail may have features and the stucture of the ion tail can change over time due to interactions with the solar wind. These features often extend over thousands of kilometers. Small telescopes equipped with CCD cameras can often achieve a pixel scale of 1 arcseconds per pixel, allowing coma or tail features larger than 1000km to be resolved.
Interestingly, the mission received hand-sketches by visual observers that show the existence of jets during the comet's apparition in 1983. One set of sketches was made in April, 1983, about three months before perihelion. Another set was made in July, 1983, only one month before perihelion. Additionally, the impact is expected to make an active area on the surface of the nucleus. Will new jets form in the days, weeks, or months before and/or after the encounter? Again, STSP observers have the ability to continuosly monitor the comet for jets and outbursts by obtaining broadband-VRI or unfiltered images. To look for pre-perihelion jet activity, the comet should be imaged from March through June, 2005. To search for post-impact jets, the comet should be imaged from July through about October, 2005.
As with the coma, small telescopes will be able to resolve gas and dust structures in the comet's tail(s). Wide-field broadband-VRI and unfiltered imaging will provide information about the spatial and temporal changes of the tail(s). These observations can begin as early as November 2004 and should continue through October 2005.
Outbursts from the coma. It is not known if comet Tempel 1 undergoes outbursts. Also, the new active area that is expected to form on the nucleus after impact may cause outbursts of gas and dust. Therefore, STSP participants can monitor for outbursts, through broadband-VRI and unfiltered imaging of the coma, beginning as early as November, 2004 and continuing through 2005. Observations should be make every 5-7 days for several months since outbursts are sporadic and tend to last only several days.
Changes in gas coma through narrowband photometry and spectroscopy. Amateur astronomers are advancing into the fields of narrowband photometry and spectroscopy with small telescopes. Narrow-band and spectroscopic studies of the coma capture information about the production of molecules such as CN, C2, and OH. Therefore, the STSP will accept any narrowband photometric and spectroscopic measurements made by participating observers.