Next: 4.2 Photographic Archives
Up: 4. Conclusions
Previous: 4. Conclusions
The organizational efforts needed for a VI campaign depend greatly on
the circumstances of the apparition. In particular, the predicted
brightness of the VI will be decisive in determining whether dedicated
time on large telescopes will be necessary, or whether smaller
instruments can be used. A comparatively large community of
professional and non-professional asteroid observers has been
successful in the follow-up of NEAs that are generally brighter than
V=20. So, when a VI is brighter than V=18, this community can
perform the necessary observations, but issues of validation and
coordination will be more challenging than if a few experienced
professionals with very large instruments are involved, as would be
necessary if the VI is fainter than V=18.
Given the special responsibility in the validation of a negative
observation, we suggest a few general guidelines for any VI search:
- 1.
- At least two independent observing teams using two different
facilities should be involved in the search for each VI around the
same time. The allocation of observing time should be sufficient to
take into account bad weather conditions. It may be advisable to get
confirmation of the negative observations on a second night from one
of the two teams.
- 2.
- The observation epoch should be chosen carefully to consider
factors such as the expected galactic latitude, solar elongation, and
brightness, as well as the lunar phase. Observers must be very careful
if the VI is expected to move rather slowly (5-10 arcmin/day or less)
to ensure that it does not remain hidden by any star glare throughout
the whole or most of the exposure time. Confusion with field stars is
less of an issue if multiple exposures with the same instrument are
available.
- 3.
- The observers must be able to detect objects two
magnitudes fainter than the nominal one expected for the VI, taking
into account trailing losses due to the asteroid's apparent motion, as
discussed in Sec. 3.3. This ``safety cushion" should be
adjusted on a case by case basis, depending on the photometric
accuracy of the observers in the discovery apparition and on the
magnitude consistency observed. The limiting magnitude needs to be
calibrated for objects with a specific motion rate. For some
long-lost objects discovered photographically it may be advisable to
extend the factor of safety to three magnitudes. To validate the
capability to detect at the level needed, the observer could be
required to measure the position, taken at a short time interval, of a
known asteroid near the VI which is somewhat fainter than the
predicted VI magnitude.
Next: 4.2 Photographic Archives
Up: 4. Conclusions
Previous: 4. Conclusions
Andrea Milani
2000-06-21