Sunday, June 27, 2004

Of Venus and Iridium flares...

It's always pretty cool how fast Venus goes from the evening sky to the morning sky during it's Inferior conjunction (when it is passing close to the Sun while on the same side of the Sun as Earth is - Superior conjuction is the opposite, when it is on the other side of the Sun). Remember just a couple weeks ago it was transiting the disk of the sun. Already it is far out from the Sun and easily visible in the morning sky. It should be able to be seen in the daytime again soon too. When it's near its maximum elongation, it is not too hard to pick out in broad daylight or at least just after sunrise or before sunset (depending on which side of the sun it is on). My friend Dan and I used to stop next to the building we worked in on our way back from lunch and try and see it when it was on the evening side of the Sun. Blocking the bright sun using the building cut the glare enough to make it a bit easier. We succeeded as often as not and it was always fun to see who would find it first. It helped to have a fresh set of glasses with the best prescription to make Venus as sharp as possible....

Have you ever seen an Iridium flare? Iridium satellites were launched a number of years ago as a global telephone communication network that went bankrupt (those dang cell phones took over that market!). The spacecraft are kept precisely oriented so that the highly reflective antennae they have on them that act like mirrors reflecting the suns image and the direction of those reflections can be predicted pretty accurately. When you are in just the right path on the ground, you can see the suns reflection off those panels (the closer you are to that path on the ground, the brighter the flare appears). Last night, I was getting ready to observe on Kitt Peak when I watched a flare predicted to be magnitude -8. That's about 25 times brighter than Venus appears in when it is at its brightest. I saw the satellite approach the predicted location as it slowly brightened and for about a second or two, it was really impressively bright. To see when the next Iridium flare is visible from your location, check out the Heavens Above webpage. Just select your location and click on the link to get Iridium flare predictions for the enxt 24 hours or 7 days (or if you think you saw one last night, there's a link for that too). You can enter your location more precisely if you know it (for example, if you have GPS unit and can measure your latitude and longitude). Iridium flare predictions are pretty location specific, so if you can enter a more precise observing location, you will get a better prediction. When you get a page of predictions, they will list the date and local time (set your watch to WWV if you can!), the Intensity (the smaller the number - i.e. the more negative the number - the brighter it will appear. Venus at its brightest is about magnitude -4.5), the Altitude (how high up in the sky it appears with 45 degrees halfway up, and 90 degrees straight over head) and the Azimuth (0 degrees is due north, 90 degrees due east, 180 degrees due south and 270 due west), the distance you would need to move to put yourself along the path of the flare center where the flare would be at its brightest, the Intensity at the flare center and finally which of the Iridium satellites is involved.

To come full circle with Venus (remember I mentioned you can see it in the daytime if you know where to look), the brightest Iridium flares can also be seen in the daytime! The observation is difficult and you need to not only be able to know where to look but to know when to look. The predictions tell you that the flare will occure at some altitude and azimuth from your site and it is very difficult to estimate just where 57 degrees altitude and 84 degrees azimuth is up in the sky without any other sorts of reference points. If you are patient and wait for a daytime flare that is at almost 90 degrees altitude, that is straight overhead and is probably the easiest place on the sky to find in the daytime. And with the sky a bright blue, even a -8 flare is not terribly easy to see, but if you manage it, it is quite a satisfying observation! Start with some night-time flares first, though!


Saturday, June 26, 2004

A great week in Space

Did you notice the excellent events in Space this week?

Early on Monday morning SpaceshipOne rocketed to above 100 kilometers altitude, making it the first privately flown manned spaceflight.

Meanwhile out near Saturn, the Cassini spacecraft is nearing its target, flying past its first Saturnian satellites as it prepares for the Saturn Orbit Insertion maneuver on June 30 (now less than a week away!). A lot of my friends are crossing their fingers that the 96 minute rocket engine burn will go off without a hitch and the spacecraft will drop into orbit to begin an exciting mission to unlock the secrets of the 2nd largest planet in our solar system. Early results from the flyby of the Saturnian moon Phoebe suggests that this moon originated in the Kuiper Belt beyond Neptune. If this is confirmed, it is the 2nd closeup look at what one of those distant objects is like - Voyager 2 flew past Neptune back in 1989 and got a closeup look at Triton which may well have originated there as well and is very similar in size and distance from the Sun as Pluto.

On Mars, a couple of hardy little robots are expanding our knowledge of the red planet with new discoveries daily. At the base of the Columbia Hills, the Spirit rover discovered Hematite in an unusual looking rock nicknamed appropriately The Pot of Gold. Meanwhile, halfway around the planet, Opportunity has been carefully creeping farther down into the Endurance crater, studying the rock outcrops there.

Back on Earth, it still seems like forever since we last saw a Space Shuttle launch, but NASA has just announced a reorganization that hopefully will help it to achieve the lofty Space Exploration Initiative goals.

This is my first blog - I'm planning to focus my posts here on Space mostly, since I'm a regular Space Nerd. My interest in science grew out of watching the Apollo Astronauts explore the moon when I was a child, so the nickname I'm using is appropriately "ApolloGeek" since I love to study every tiny detail of the Apollo space program and look forward to the day that we again have humans walking on the Moons surface and kicking the rust colored soil of Mars as well.