All of the major telescopes of the National Optical Astronomy Observatory (NOAO) on Kitt Peak are observing comet Tempel 1 for several nights before and after the planned Deep Impact event. Indeed, by the night of July 8, Kitt Peak National Observatory will have been used for 43 nights in 2005 in scientific support of the planned collision at approximately 10:52 p.m. local time on July 3 between the icy comet and a special probe released from the main Deep Impact spacecraft.
The coordinated observing team on Kitt Peak’s major National Science Foundation telescopes consists of Tony Farnham, Matthew Knight and Rob Swaters from the University of Maryland, and Beatrice Mueller and Nalin Samarasinha from the NOAO scientific staff.
The team’s goal was to monitor Comet Tempel 1 on a monthly basis, with two main purposes. “First, we need to figure out the fundamental physical properties of the comet, so that we can provide information to the Deep Impact mission science team that can be used in both the long- and short-term planning of the mission,” Farnham says. “By observing Tempel 1 every month, we can determine how it changes with time, which helps us predict what it will be doing at the time of impact. Second, we need to follow its behavior under normal circumstances, so that when we observe it after the encounter, we can separate out the changes that result from normal variations in the comet from the changes that are caused by the impact.”
Between January and June 2005, the team had a total of 24 nights of observing time at the Kitt Peak 2.1-meter and Mayall 4-meter telescopes. “During these observing runs, we imaged the comet using a broadband and several narrowband filters, which allow us to isolate the light from different gases and from the dust,” Farnham explains. “The resulting images can be used to study the structure of the gas and dust in the coma, as well as allowing us to use the brightness to measure how much gas and dust is being produced. We used the images obtained between January and May to determine many of the rotational properties of the nucleus, and used that information to predict how the nucleus will look to the Deep Impact spacecraft during its approach.”
Around the time of impact, the team has observing time on three different Kitt Peak telescopes: eight nights at the 4-meter telescope, which will be used for narrowband imaging, five nights at the WIYN 3-5 meter telescope for optical spectroscopy, and seven nights at the 2.1-meter to obtain infrared images.
Mayall 4-meter telescope at Kitt Peak
On the night of impact, Farnham will be at the Mayall 4-meter telescope taking images of the comet with narrowband filters to look for changes in the comet after the event. Potential changes include increases in the amount of gas and dust that is being produced, immediate changes in the structure of its coma (the comet’s surrounding cloud of material) as any crater ejecta expands away from the nucleus, and any long-term changes that occur as a result of fundamental changes on the nucleus.
Kitt Peak 2.1-meter telescope
Matthew Knight and Rob Swaters of the University of Maryland will be observing the Deep Impact encounter with the 2.1-meter telescope using the SQIID camera from two nights before impact until five nights after impact. This will be a unique part of the worldwide observing campaign, as SQIID is the only camera which will take simultaneous images in the J, H, and K bands. Comparison of the relative fluxes in these bandpasses will probe the temperature evolution of the coma in the days after impact.
Knight will have spent 18 nights observing Tempel 1 at Kitt Peak National Observatory this year (plus eight additional nights in which data on Tempel 1 were obtained during a different project.)
WIYN 3.5-meter telescope
Beatrice Mueller and Nalin Samarasinha of the NOAO scientific staff will observe at the WIYN telescope from July 2 - 6, using the Densepack fiber spectrograph. They expect to observe the emission lines of molecules such as CN, C2, C3, CH, and CO+.
“We can study the relative abundances of these species and see if and how they change. These are daughter speciesthat arise from subsequent interactions after the material leaves the comet,” Mueller says. “With Densepack, we can sample the coma simultaneously and see if all these lines originate from the nucleus or if some are from distributed sources.
“Together with the University of Maryland group, we have observed the comet every month for at least four nights per month with imaging in broadband and narrowband filters,” she adds. “The narrowband filters are placed where emission lines are, and so-called continuum filters measure in between the lines and are best for studying materials such as dust.”
Astronomers are also excited about the possibility of seeing “serendipitous emissions” from the comet of chemical species created by the energy of the comet impact.
This group of professional astronomers will be augmented by a special public program on Kitt Peak for 50 people during the night of the event, which is now sold out.
Located 55 miles southwest of Tucson, AZ, Kitt Peak National Observatory is part of NOAO, which is operated by the Association of Universities for Research in Astronomy (AURA) Inc., under a cooperative agreement with the National Science Foundation.