March 2007 Archives

A bit more on Lovejoy

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Just a bit more information on comet Lovejoy (C/2007 E2): it has indeed reached perihelion (closest distance to the Sun) yesterday, but it will continue getting closer to Earth until 26 April (or, rather, Earth is getting closer to it). At that point, it is expected to reach a magnitude of just under 8; that is, it will be a binocular object on relatively dark skies, but there's no chance of viewing it with the naked eye.

Orbital info, finding charts and a graph of the expected magnitudes are available from Seiichi Yoshida's page.

Comet Lovejoy

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A new comet was discovered by an Australian amateur astronomer: comet 2007 E2, aka "Lovejoy" (named not after the Reverend, but the discoverer, Terry Lovejoy). The Possum Observatory (John Drummond, in Gisborne, New Zealand) has a bit more information and a picture.

NASA has a simulation of the orbit of this comet, but I don't know how accurate it is at the moment. It seems to indicate that it will swing by relatively close to Earth (0.445 AU) on 25 April, although it will be over 1 AU away from the Sun at the time; I have no idea (and I don't think anyone does) of how bright it will be at the time. Judging by the fact that it is, right now, very close to its closest approach to the Sun (at 1.1 AU) and it is a 9th magnitude object (although with a somewhat long, if faint, tail), I wouldn't expect it to become a particularly interesting object visually.

Holidays

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(a slightly edited version of this article will appear in the April/May issue of "Crux", the magazine of the Astronomical Society of Victoria)

Canberra Space Centre, DSS-43I had some days off over the end-of-year holidays, and I took the chance to visit some "astronomically important" places in and around Canberra. So, let me tell you about how my trip went...

The first stop was at the Canberra Deep Space Communications Centre (aka Canberra Space Centre), just outside Canberra. This is one of the three deep-space communications centres used by NASA to communicate with unmanned probes across the solar system (the other two are near Goldstone, California, and outside Madrid, Spain). This means that this is a two-way communications complex: it receives data sent by the probes, and also sends instructions out to them.

This space centre is home to the largest parabolic antenna in southern hemisphere, DSS (Deep Space Station) 43, with a 70-metre reflector dish (which, I must say, is an impressive sight). It also hosts DSS 46, the 26-metre antenna that was originally at Honeysuckle Creek and, at that location, received the first images of Neil Armstrong walking on the Moon (more about this below). Two other large antennas are at the site, DSS 45 and DSS 34, both measuring 34 metres across.

Prototype of the Mars RoverThe Canberra centre is involved with most of the current high-profile NASA missions around the solar system (and outside it); on a typical day, the centre's antennas will talk to the Cassini probe around Saturn, the Mars rovers Spirit and Opportunity, the new Mars Reconnaissance Orbiter, the Sun-observing SOHO satellite, the ESA's comet/asteroid mission Rosetta, the new 3D Sun imaging STEREO satellites, the two Voyagers... and the list goes on.

Close to the antennas there is a small visitors centre with some very interesting material on display. The "rarest" of the pieces on display is a small piece of the Moon (it looks just like a regular rock, to be honest — perhaps a little darker than usual). There are also display pieces about many of the probes tracked by the centre, including Cassini, the Voyagers and the Mars rovers (they have one of the testing prototypes of the rovers on display, so you can get an idea of how large they are).

Model of the Space Shuttle, visitors centreThe CDSCC is also used to communicate with the Shuttle when it is in orbit, so it has several Shuttle-related items on display, including "used" heat shield tiles and samples of food used on board. Another display case features the Stardust mission, including a small piece of aerogel it used to capture fragments of cometary and interstellar dust. I honestly wish I could have the chance to pick up the aerogel and "feel" it...

Right afterwards, I tried visiting the Mount Stromlo observatory, but it was closed to visitors until after the holidays, so it was not to be.

The next day, I drove from Canberra up to Parkes, NSW, to visit the famous "Dish". This is a four-hour trip, so it's not quite a "casual drive"; it was definitely worth it, though. The Parkes Observatory is in country New South Wales, 20 km north of the small town of Parkes (which is also known for the Elvis Festival that happens there every year) in the middle of farm fields. The large antenna makes for a great sight from the road, by the way. The location was chosen because of the proximity to a small city, the low level of radio noise and the decent weather (which, for a radio telescope, means "low chance of high winds"; rain and cloud are mostly not relevant).

Differently from the Canberra Space Centre, the Parkes Observatory is a scientific installation; a radio telescope, not a communications centre. This means that it is an "one way" antenna (it receives signals, but doesn't send anything back); it is also used mostly to listen to naturally-occurring radio signals, rather than signals sent by man-made probes.

The Parkes Dish, seen from the roadThe 64-metre Parkes dish is the second largest antenna in the southern hemisphere, behind Canberra's largest dish. These antennas are likely to continue to be the first and second largest for the foreseeable future; probably until they are decommissioned, in fact. The reason for that is that it's no longer financially acceptable to build such large dishes; it is better to build several small dishes, join their signals together and treat them as one very large dish. This was not possible in the past due to the difficulty in synchronising the signals received by the different dishes, but advances in technology made this possible. So, it's very unlikely that dishes larger than 20 meters in diameter will be built in the future, anywhere in the world.

One interesting difference between the Parkes dish and the DSS dishes is that the one in Parkes moves around more quickly (and more often) than the ones in Canberra; it can move slowly to track an object across the sky, but it can also move quickly to "change targets", which it does several times a day; its top speed is of 24 degrees per minute horizontally.

As is the case in Canberra, there is a visitors centre close to the telescope with research information on display. You can read about the current research tasks of the dish and about famous results it achieved in the past. And, of course, they have lots of information on the participation it had in NASA's Apollo 11 mission to the Moon.

Anyone who has seen the movie The Dish knows that the first images of humans stepping on the Moon were received in Australia; that part is true. However, it was not Parkes doing that: as is hinted in the movie, the Moon was indeed too low in the sky at the time the astronauts walked out of their capsule. The first images were then received at the old Honeysuckle Creek station, near Canberra; Parkes started receiving images a few minutes later, and from that point on Parkes' images were broadcast to the world (the quality was better because of the larger dish).

I should mention, also, that the Dish Café, located near the visitors centre, serves a very decent burger and has several astronomically-themed dishes in its menu. I do recommend, however, that if you go there in the summer you avoid sitting close to the windows; the flies there are very, very annoying.

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