--- Patrick Wiggins <paw@trilobyte.net> wrote:

Unfortunately at the time of impact (very early on the morning of 4 July) the comet it will not be terribly well placed for viewing from Utah but it will be visible.

Although the impact itself may not be well-placed, the Deep Impact team is soliciting participation from the advanced amateur community in a program to continuously observe the VR magnitudes of the comet up to the date of the impact. With the new Big Scope and the existing Ealing, this may be something for club members to consider between when the current rain clouds clear and July. The Deep Impact mission's website solicits participation in an observing program by advanced amateurs with high-end CCD gear and V and R band filters. The following is an excerpt from the Deep Mission Impact amateur astronomer program website at - http://deepimpact.umd.edu/stsp/ and at http://deepimpact.umd.edu/stsp/equipreqs/index05.shtml regarding equipment requirements: ========================= "Telescope Requirements Minimum aperture: 9.5 inches or 24 centimeters Suggested focal length: f/4 or f/5, but more important is to match the CCD's pixel resolution to the seeing and to the telescope's image size while retaining a large field of view! CCD Requirements One of the top-notch, commercial CCDs such as: Apogee HiSIS SBIG Meade Pixel resolution of 2 arcseconds or better. Filter Requirements Use standard photometric filters (Kron-Cousins, Johnson, Bessell) V and R to make observations of the comet. These filters allow us to do scientifically meaningful studies of Comet 9P/Tempel 1. If your system has an infrared cutoff filter, it must be removed when you observe with photometric, broadband, V and R filters! If you do not have these types of filters, do not lose hope! You have some options: . . . . ========================= The purpose of the small telescope observing program is described in Deep Impact Small Telescope Science Program webpage as: "The main objective of the program is to provide continuous monitoring of 9P to complement data acquired at large telescopes. Many observers who control their own observing time can contribute to our goal for continuous coverage. The program is interested in receiving photometric quality, broadband R, CCD images of 9P as well as spectroscopic observations. These data will help scientists understand and model the activity and dust environment of the comet before, during, and after the mission excavates a crater in the nucleus in early July 2005." For those just interesting in following the comet between now and July 2005, the Deep Impact mission also publishes useful observing guides and ephemeredes at - http://deepimpact.umd.edu/amateur/charts/index.shtml

Personally I find it a little hard to imagine how lobbing a couple of hundred kilos of copper into a comet measuring some 4 x 4 x 9 km is going to throw up enough dust to brighten it that much.

In October 2004, I became interested in the comet's mass and contacted the public affairs officer at the Deep Impact Mission team at the University of Maryland. The following was public affair's officer's answer relayed from the mission team: ========================= "We don't know the mass of comet Tempel 1 at this time. We don't even know its size very accurately yet. We can estimate its mass by assuming a density and dividing the Density by the volume and compute a mass. M=D/V. Our best estimate is anywhere from 0.1 - 2.5 x 10 exp 14 kg. We should be able to constrain this value better after we analyze images of the impact and have a more accurate shape model of the comet. The goal of the Deep Impact mission is to determine the composition and structure of the interior of the comet. We will arrive at a more accurate value of the mass in the process." ========================= That's a mass estimate range for Comet 9P/Tempel 1 of between: 10,000,000,000,000 kilograms and 250,000,000,000,000 kilogram. In contrast, the Deep Impact Mission homepage recites the mass of the kinetic impactor as: 370kg - 820 lbs http://deepimpact.umd.edu/science/cratering.html Traveling at 10 km/s, the 370kg impactor spacecraft will obviously have a significantly greater effective mass - but still will excavate a crater about 200 meters by 60 meters deep. Once vaporized, will result in a pretty large volume of dust that can act as a reflector. Another Deep Impact Mission webpage describes a TNT equivalency resulting from kinetic impactor's collision: ========================= "When an impactor strikes a target, it has a great deal of kinetic energy (proportional to the object's mass and the square of its velocity). For example, the impactor spacecraft for the Deep Impact Mission has a mass of 370 kg, and will be traveling at a velocity of 10.2 km/s. This means its kinetic energy will be 19 gigajoules (GJ), which is about the equivalent of the amount of energy released by exploding 4.8 tons of TNT, or about the amount of energy used in an average American house in one month." ========================= http://deepimpact.umd.edu/science/cratering.html The dust cloud will allow the study of the unknown chemical composition of comets with spectroscopy on the impact's ejecta from a spectrometer mounted in the nearby Deep Impact fly-by satellite and based on the resulting shape of the crater. Much of the ejecta will settle back down on the comet. Depending on the unknown composition the ejecta, the resulting long term change in the reflectivity of the comet is anybody's guess. For more details, see - http://deepimpact.umd.edu/science/cospar-ms.pdf http://deepimpact.umd.edu/science/objectives.html - Canopus56 P.S. - Should you receive any general public questions along the line of "Will the comet change it's orbit and crash into the Earth?", the impact will change orbital veloicity of the comet by a few meters per second. This is less than the 30 m/s a second that the comet's velocity varies each year as a result of gravitational tidal interactions with Jupiter. Any minor change in its orbital velocity will be dampened out by interactions with Jupiter. __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/