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Jay Pasachoff

More Venus transits in 2012

Posted by Jay Pasachoff

07-06-2012 16:44 CDT

Topics: planetary astronomy, Hubble Space Telescope, transit of Venus, Cassini

Introduction: transits of Venus are rare events for people bound to Earth. James Burke tipped me to the story about plans to observe transits of Venus as seen from other planets, which, of course, happen on different dates. Jay Pasachoff kindly explained his proposals for such observations to me in an email, which he has permitted me to reproduce below. -- Emily Lakdawalla

I am pleased to supply more information about our hopes and plans for observing transits beyond the one of Venus as seen from Earth on June 5/6, for which I have a grant from the Committee for Research and Exploration of the National Geographic Society.  

As you know, David Ehrenreich and Alfred Vidal-Madjar in France, and others, [had] Hubble Space Telescope time to observe the June 5/6 transit with three instruments by looking for 0.1% dips of the brightness of the three areas of the Moon at which the instruments will stare.  There will be calibration time before and after the transit. All times are about a half hour later than those for the Earth.  Glenn Schneider and a colleague tried to use a Steward Observatory telescope to do something similar for the 2004 transit, but had a ground-based telescope and inadequate time on the transit from their location.

When I learned about the Hubble experiment, I arranged to meet with Ehrenreich and Vidal-Madjar (with whom I had written a paper about interstellar deuterium about 30 years ago) in Paris right after the Division of Planetary Sciences meeting in Nantes, where Widemann and I had coordinated our mountain-based 2012 observations.  I had brought him into the analysis of the 2004 TRACE spacecraft observations that Schneider and I had analyzed and published [PDF], with the additional author Leon Golub, who had built the camera for TRACE.  Widemann provided links to the data from Venus Express.  Later, in a subsequent article, Paolo Tanga from an institute in Nice elaborated on the 2004 transit as observed from Pic du Midi, other ground-based telescopes, and Venus Express, for which I was again a coauthor along with several others.

After Widemann and I met with Ehrenreich and Vidal-Madjar at l'Institut d'Astrophysique in Paris, I was jealous of their successful proposal, so I thought about what other transit opportunities there might be.  It turns out that a transit of Venus was visible from Jupiter earlier in May, which was too soon to propose for Hubble time, with another coming on September 20.  I put together a team that involved Schneider, the French colleagues, and my former student Kevin Reardon, who is now at the Arectri Observatory.  We also included one the two main scientists who have instruments to study the Total Solar Irradiance: Richard Willson of ACRIMsat, with whom we had put together NSF and NASA proposals for the current transit. Co-investigators also include the French group with the addition of Alain Lecavelier des Etangs from Paris, and John Clarke of Boston University.

Since Schneider was instrument scientist on Hubble's NICMOS and was very experienced with making Hubble proposals, he took my first draft and supervised the major proposal--which is always a very big effort for a Hubble proposal.  There were a semi-infinite number of emails considering various possibilities, including using Jupiter's disk as a reflector and using one of Jupiter's moons.  We decided that Jupiter's disk came nearest to filling the field of view from Hubble so observing its intensity over the 9 hours of transit plus some time before and after became the major thrust of our proposal, looking for a 1/100 per cent drop in the intensity.  Io and Europa add to the orbits immediately flanking the transit, and we will use their added contribution to help in our calibration.

The proposal was submitted this spring; we expect to be notified on June 15.  It would be nice to know before I give an invited, plenary talk about the transit of Venus at the AAS meeting in Anchorage on June 11, though we probably won't.

In any case, we then looked for a transit of Venus from Saturn, and found one on December 21.  We brought Phil Nicholson of Cornell into the group because he is on the Cassini team.  At a group meeting last month, he convinced everyone (we had sent him some PowerPoints and other ammunition) to provide Cassini time for that transit, also for an 0.01 per cent effect, on December 21.

Read a followup blog entry about more planetary transits as seen from other planets >

See other posts from June 2012


Or read more blog entries about: planetary astronomy, Hubble Space Telescope, transit of Venus, Cassini


Mike: 06/08/2012 02:50 CDT

Just a question. What about also looking at transits by Earth and Mars from Jupiter, and transits by Earth, Mars, and Jupiter from Saturn? Time frame too long?

Emily: 06/08/2012 01:03 CDT

That's a good question. I'll ask!

bware: 06/09/2012 07:54 CDT

Thiking 5 years down the road if our LightSail S/C (Spacecraft) Flight Tests 1 & 2 prove solar sailing works then we can stage our own eclipses. What we would need would need to do is place our S/C behind the planet we want to perform the eclipse. With a mounted camera, transmit ability and memory we could fly a trajectory creating the eclipse and in the case of Jupiter setting the S/C on a free return to Sol (for more light energy) as a safety factor. (assuming the orbital mechanics would be possible). Since we have 2 S/C, no LV yet but do have a greenlight for launch from NASA, and talk of the 3rd S/C doing a solar mission, this could be for mission number 4. Regarding rockets for our S/C I have entered an idea in another guest blog. In short words it involves speaking with SpaceX and Orbital Sciences Corporation. Since you all sound serious about this I thought I'd drop this idea to you. Remember as late as the early 1950's flying in space was preposterous and only for lunatics who could not 'get a real job' in real life. That is the way I was raised but I never bought into it, much to my parents grief!

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