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Observations of Transits of the Inner Planets within the Field of View of UVCS

 

The UVCS can be used to map neutral species in the outer atmosphere and atmospheric tail of Venus (and possibly) Mercury at the occasions when these planets cross the field of view of UVCS.

Obviously one would have to look at neutral or weakly ionized species. The prime target would be Ly--. Other lines are of similar interest, eg. C III, N II, O II and O III, He I for Venus which has a thick atmosphere. For Mercury one would like to look at lines for Na I, Na II and K I and K II (Na has been observed previously, K might also exist in sufficient amounts to be detected).

Paul Wild and Urs Hugentobler from the Astronomisches Institut, University of Bern, have made some preliminary computation on possible occasions for such observations. There seems to be only one occasion when Venus apparently approaches the Sun to less than 5 R within the next few years. We are lucky as this will already be on June 10, 1996 at 16h UT when the distance (as observed from the Earth) will be 1.9 R. Then there will be opportunities every eight years. Of course one should make the computations using the trajectory of SOHO but there will not be a large difference as SOHO remains within 6 10 km from the Earth--Sun line. Other lower conjunctions of Venus with distances < 6 R will be at the following dates:

Lower conjunctions of Venus with Sun

we could hopefully produce a picture of the Venus atmosphere with good resolution. Furthermore, one could even do some good science with such a picture. It has to be anticipated, that the instrument will no longer work, for the second and third encounter.

The upper conjunctions when Venus could pass our field of view but will be much farther away (behind the Sun) have also been added.

Upper conjunctions of Venus with Sun

Lower conjunctions of Mercury with Sun

Upper conjunctions of Mercury with Sun



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Next: Ground-based Observations in Up: Examples of UVCS Previous: UV Observations of



Peter Smith
Fri Jan 17 12:11:15 EST 1997