As of mid-2007 when a major update of the HSpot database was made, there were already more than 360 000 solar system objects (SSOs) that had been catalogued. Since then this number has increased rapidly. HSpot does not have the capability to include this complete database, nor are the majority of these objects observable by Herschel for reasons of sensitivity and, in the case of many satellites, also because Herschel lacks the spatial resolution to resolve them from their primary. A total of approximately 500 SSOs are included in the database. These are listed in Appendix C, Solar System Objects that have ephemeris information in HSpot. HSpot at present uses a static ephemeris from the JPL Horizons system; that is, it does not update, even if the orbit file in Horizons is improved. This will potentially be a problem for planning observations with some comets and many NEAs [please note that our Mission Planning software does use an active ephemeris for scheduling purposes]. All the orbit files for SSOs were updated for launch on May 4th 2009 and will be updated on a regular, although probably not monthly, basis.

Note

If you need to observe a SSO that is not included in the HSpot database, for example, a newly discovered object, please contact Helpdesk (http://herschel.esac.esa.int/esupport/) at the Herschel Science Centre to have it included. A significant update in HSpot since the initial call for proposals has been an improvement in the way that ephemeris files are handled so that they are now no longer part of the HSpot build, so new objects can be included far more quickly and easily.

Warning

For close approach objects, the ephemeris in HSpot will usually be sufficiently accurate to plan visibility, but not to schedule observations. For campaigns involving close approach objects such as 103P/Hartley 2, or 45P/Honda-Mrkos-Pajdusakova, special updates to the ephemeris will be required as close to the date of observation as possible. Experience shows that for these objects only when radar observations are available is the ephemeris accurate enough for Mission Planning purposes at HSC.