Footprint Services at a Glance

� To visit Footprint Services, go to http://www.voservices.net/footprint

� Discover sky coverage of various observations by clicking on the search link

o Object search (default)

� Returns footprints that cover the specified objects

� Uses NED or Simbad for name resolution

o �Keyword search

� Runs against metadata, e.g., name, description, comment

� Uses logical operator on the right to accommodate advanced queries

o Other options include lists of positions and search by region of interest

� Select Object search for this exercise

o Click the Search button to find regions that cover, say, Messier 51

o The results are shown graphically on multiple pages

o Click on any of the footprints for details, say SDSS DR4

� To visualize your choice, click the Plot button

� The default options on the next page will show a stereographic projection

� Change the projection to �an all-sky Aitoff view, and you should see this:

o

To save the footprint in various formats, click the Download button

� Go back now to search for keywords

o Enter the words SDSS and GALEX and select the logical OR operation

o

Click on Next to get to the following page of results

o Select the first two footprints on that page: GALEX GR3 NGS and SDSS DR6

o Change the process method to Plot in the roll-down menu and click Next >

o Take the default setup and visualize both regions on one image:

o

Click on the image anywhere to re-center the projection

� Let us now create a new custom footprint

o Click on the editor tab on top of the page

o Then click the New button

o To create a polygon, pick the first button

� Specify the corners of your convex polygon and click OK

o To take the union of this polygon and circle, click Union and pick Circle

� The default will draw a circle around one of the corners of the default polygon

� Click OK and should see this

�

The precise analytic area of this coverage is display along with some other information

� Note that you can plot, download this new region or make further manipulations on this page