C. List of Solar System Objects

From the ISO mission planning point of view the solar system targets differed from other astronomical targets. This is due to the fact that solar system objects (SSOs) have no fixed equatorial coordinates. Therefore they were identified by their names in the Mission Data Base and linked to their corresponding ephemerides. The database of ephemerides contains all outer planets, most of their moons, major comets and selected asteroids.

Observations of solar system targets required tracking of the specific object by the spacecraft via a raster observation (see Section 4.5). As the spacecraft raster option was already used for tracking there was no possibility to use the spacecraft raster mode for observations. Therefore, observations of solar system targets in the spacecraft raster mode were forbidden. Additionally, in a certain direction chopping was not feasible. Section 4.6 lists the available AOTs and restrictions with respect to observations of solar system objects. The spacecraft raster capabilities limited observations to objects with an apparent velocity of less than 2 arcminutes per hour with respect to equatorial coordinates.

There are several additional aspects specific to solar system targets (e.g. change of orbital parameters, eclipse of a moon around a planet, change of galactic background or stray radiation level, etc). Users who intend to work with ISO observations of SSOs retrieved from the ISO Data Archive should refer to the documentation available at the ISO IDC web site under:

https://www.cosmos.esa.int/web/iso ISO Explanatory Library ISO Satellite

on `Data reduction and analysis of SSO observations' for further information.

SSOs observed in the solar system tracking mode have associated numbers in the Mission Data Base that were used to identify these targets to the mission planning system, and therefore the ISO Data Archive (IDA) contains both the target name and the associated number in this list, either of which can be used in searching. Table C.1 gives SSO names and ISO generic numbers for all objects observed in this mode during the mission.

Note that other SSOs may have also been observed in non-tracking mode (i.e. fixed pointing), in which case they will appear in the archive solely by the name given by the observer. Non-tracking mode was used when looking at objects such as dust trails, the zodiacal light and Pluto. These sources are, of course, not included in Table C.1.

In addition, many other SSOs have been seen serendipitously in deep ISOCAM images, in large survey programmes, in the CAM parallel survey and in the PHT serendipity mode.