Viewing With Satellites

In 1882, Astronomer William Harkness wondered what scientific advances we might be using in 2004 to view the transit of Venus while the 'flowers bloom in spring'. On June 8, 2004 you will be able to watch this transit as Harkness hoped, not just from ground-based vantage points like the ones which Harkness imagined, but from an entirely new vantage point…Space!

NASA's TRACE satellite, which has been keeping watch on solar flares on the Sun, will be in the perfect location to see the entire transit of Venus, unobstructed by clouds, trees or tall buildings. From its perch in orbit around Earth, some 330 miles above the surface, it will see Venus slide across the face of the Sun, and show details on the solar surface that will also dazzle and amaze. If we are lucky, we may even catch a flare or two exploding into space with the energy of a thousand hydrogen bombs.

If you want to view the TRACE images as they are posted, visit their web page at http://vestige.lmsal.com/TRACE/transits/venus_2004/ This page has links to their Mercury transit image archive too, plus links to other Venus Transit resources.

"As seen from Earth the planet Venus will be visible in front of the Sun for more than 6 hours. From SOHO's perspective, however, 1.5 million kilometres from Earth and slighly off the Sun-Earth axis, the planet Venus will not pass in front of the Sun but glide slowly just beneath the solar disk as shown in the illustration above. However, it will be visible against the emission from the diffuse corona."

"So the transit will be closely watched by several instruments on board SOHO: LASCO, UVCS, SUMER, EIT, and CDS. Venus is expected to appear in the LASCO C3 field between June 3 and June 13, clearly visible on our real-time images page ( http://soho.nascom.nasa.gov/data/realtime/realtime-update.html). Special EIT images and movies of the transit (cropped on-board to increase the cadence of the images) will be available on this web page. Due to the cropping and other factors, the special images will not be picked up by the standard real-time image processing."

Teachers and Students, if you are looking for a very unique way of relating the transit of Venus to your studies of the scale of the solar system, why not use the TRACE data to calculate the Astronomical Unit?

NASA's IMAGE satellite, in participation with TRACE, has developed a step-by-step classroom activity that uses the TRACE Mercury and Venus transit 'montage' images to calculate the distance from Earth to Mercury and Venus. From this you can calculate the distance from Earth to Sun (the Astronomical Unit) to within a few million miles accuracy! All you need is a millimeter ruler, a pencil and a calculator. If William Harkness had had this data, he would have been astonished at how easy it is to get the right answer. Of course, the satellite only cost a few hundred million dollars!!

Here are the links to the Mercury and Venus transit activities at the IMAGE web page:

1. Calculating the Astronomical Unit during a transit of Mercury using Satellite Data
2. Calculating the Astronomical Unit during a Transit of Venus using Satellite Data

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