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In this Cookbook, we have not yet tried imaging a moving target. Spitzer
can observe Solar System targets, by tracking in linear segments at rate
up to
, while superposing any requested
mapping motions onto the track.
In this chapter, we will describe the steps needed to create an AOR for a moving target. Because imaging with MIPS and IRAC have been covered thoroughly in earlier chapters (see §4, §5, §9 and §10), we will not spend as much time on those aspects of these observations here; this chapter is meant primarily to give an example of observing a Solar System object.
We will plan an observation of the Centaur 5145 Pholus. Centaurs are
objects whose perihelion is outside Jupiter's orbit (5 AU) and whose
semi-major axis is less than that of Neptune (30 AU). Pholus is thought
to have a size of about 190 km and an albedo of about 0.04. When
discovered, it was the reddest object in the Solar System, a
characteristic that is believed by some to be due to the presence of
organic-rich materials on its surface. Observations of these kinds of
objects at MIPS wavelengths will help to constrain albedos and diameters.
They are too faint for IRAC, except perhaps at 8
m, the very longest
IRAC wavelength.
The collection of Spitzer resources for observers can be found in the Proposal Kit area of the SSC website:
This includes (among other things) an overview of things Solar System observers should know about observing with Spitzer, and a document called ``Horizons Tips for Spitzer Solar Systems Observers.'' The JPL Horizons ephemeris tool has been modified to allow specification of Spitzer as a coordinate center. This is valuable, because although Spot can provide basic information on Solar System objects to help you plan, specify, and visualize your observations, it cannot provide detailed object-specific geometric information (e.g., planet phase, range, solar elongation, ephemeris positional error) which may also be important for planning your observations. Instructions on how to specify and request this sort of detailed Spitzer-centric information for your target can be found in the Horizons Tips document.
Horizons tips also includes instructions for a new tool, ISPY, which allows you to query for known Solar System small bodies in your Spitzer data, at a given time. The ISPY capability has also recently been incorporated into Spot visualization. To visualize the position of other known moving targets in your planned observations (regardless of whether your target is fixed or moving), use the Spot ``overlay'' option ``Show all moving objects at a given date''.