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Hubble's gyros

The Hubble Space Telescope (HST) uses a collection of gyroscopes to maintain it's orientation in space while it observes the Universe. It is designed to use three of these to point accurately and was launched with a total of six - three for operation and three for backup. Over the 15 years Hubble has been in orbit, several of the gyros have failed and been replaced by space shuttle crews on servicing missions. Currently, two are broken, three are operating, and one is switched off as backup. If another two fail, Hubble will not be able to point correctly and science operations will come to an end.

After the Columbia incident in 2003 NASA have decided not to send the final servicing mission to Hubble due to safety concerns (they may change their minds again, we'll have to wait and see). This means that the two dead gyros will most likely not be replaced. To try and extend the life of the HST, engineers have been working to come up with other ways to keep Hubble pointing in the right direction. Their solution is to switch off another of the gyros, leaving Hubble operating on just two, and use the fine guidence sensors to add some of the missing information.

This week Hubble begins science operations in this two gyro mode. This new mode of operation has been throughly tested on the ground using models of the telescope so the engineers are confident that it will work and not impact on the quality of science astronomers are able to perform. It should also prolong the life of the telescope allowing operations to continue into 2008 without another servicing mission.

Posted by Megan on Wednesday 31st Aug 2005 (19:52 UTC) | Add a comment | Permalink

More on UB313

Mike Brown and his collaborators have today posted the discovery paper for 2003 UB313 on the astro-ph archive. In the paper they describe the discovery technique used to find this and other minor planets they have previously found, as well as photometry and spectroscopy of UB313's surface.

The paper has a lot of interesting facts and figures about 2003 UB313 such as the fact that it doesn't reach perihelion (the point in the orbit where it is closest to the Sun) until 2257, and even then it is still more than 38 times further away from the Sun than the Earth is. The photometry they have done shows that it's diameter is 2250 x pr-1/2 km, where p is the albedo, through a particular filter known as R-band. This is how they know that UB313 must be bigger than Pluto. If you assume an albedo of 100% (a perfect reflector) then this relationship gives a diameter larger than Pluto's. They also looked at it's spectrum and found that, although it is similar to Pluto's, there are certain differences. Both have large amounts of methane, but other molecules seen on Pluto such as N2, CO and CO2 have not been detected so far on UB313.

As UB313 has such an eccentric orbit, the temperature extremes are greater than those on Pluto. This provides a new laboratory for planetary scientists to investigate low temperature chemistry in the outer solar system.

Posted by Megan on Wednesday 31st Aug 2005 (11:39 UTC) | Add a comment | Permalink

How to find a planet

Planets may be big objects on scales that we are used to as humans, but they are really quite small and difficult to detect as they emit no light of their own. This is one reason why 2003 UB313 was only discovered recently. But if you think it is tricky finding planets in our own solar system, try looking for them around other stars. Although many extra solar planets have been discovered in recent years, most of them have been detected by methods such as photometry (a star dims as a planet passes in front of it, requires good alignment of star and planet), spectroscopy (the planet causes the star to wobble slightly which causes a slight doppler shift in the spectrum of the star) and astrometry (directly detecting the wobble of the star caused by the orbiting planet). All of these methods are most sensitive to so-called "hot Jupiters", planets much larger than the Earth which orbit quite close to their parent star.

One way of finding Earth-sized extra solar planets is to use the transit technique from space where the atmosphere causes much less of a problem. The Kepler satellite, due to launch in 2008, is a mission designed to do just that. It will observe many stars in our neighbourhood of the Milky Way watching for the tell-tale dimming of these stars caused by transiting planets. Kepler will be sensitive to Earth-mass planets orbiting at a similar distance from their parent stars as we are from our own Sun.

Another method was described in a talk at a conference in Beijing in June 2005. This is a ground-based technique which makes use of small (1 to 2 metre) telescopes located at Dome C in Antarctica. This method (decribed in the astro-ph paper) makes use of a phenomenon called gravitational microlensing where the light from a distant star is bent, or lensed, by another star which is relatively nearby. If a planet happens to be orbiting the nearer star, then it's gravitationl field distorts the image of the background star even more. The extra distortion of the light from the background star tells us about the presence of the planet even though we cannot see it directly. This extra distortion occurs without the precise alignment of the planet's orbit required for the transit technique.

To see a microlensing event you have to be very lucky. The chance of a nearby star passing directly in front of a distant star is very small, so you have to observe a lot of stars to increase the chance that you will catch one of these events. That's why the reserchers plan to look towards the Galactic centre where there are lots and lots of stars. Current microlensing searches (e.g. OGLE, MOA) observe large fields of stars very regularly to increase their chances of spotting an event.

Why Antarctica? Well, there are several reasons. Firstly, to observe the Galactic bulge you really need to be in the Southern hemisphere as it never rises very high above the horizon from here. Dome C also has very good seeing conditions which are vital for this sort of experiment. During winter you also get uninterupted darkness allowing round the clock observations, vastly increasing your chances of catching a microlensing event.

Posted by Megan on Tuesday 30th Aug 2005 (22:19 UTC) | 57 Comments | Permalink

The point of amateur observing

Recently there was a letter in Astronomy Now asking if there was a point to amateur observing any more, what with all the light pollution and the large professional telescopes regularly producing spectacular images. I replied pointing out that the discovery of supernova 2005cs in M51was made by Wolfgang Kloehr, an amateur astronomer from Germany. Many other supernovae and comets have been discovered by amateurs, and they can also provide useful data on variable stars and meteor showers. Aside from all that, it is still fun!

Ken Crawford, an amateur astronomer from California, has some pretty impressive equipment and is lucky enough to have dark skies in which to make use of it. Amongst his large collection of deep-sky observations he has photographed Sh2-188, a nebula is the constellation of Cassiopeia. It is worth having a look through his image archive as they really are very good, but here is his image of Sh2-188:


Sh2-188 in hydrogen alpha and oxygen three. Credit: Ken Crawford

Along similar lines, after a distance learning weekend a while ago, one of the students emailed me a picture he had taken of M82, the galaxy I spend most of my time studying. As a research astronomer (in training) it is great to see people taking these images. Personally, it's always nice to see that there are other people with the same enthusiasm for looking at the sky, something that often seems to be largely lacking in the world of professional astronomy.

Posted by Megan on Sunday 28th Aug 2005 (23:53 UTC) | Add a comment | Permalink

Why do astronomy at all?

This, believe it or not, is a common question at our "Ask an Astronomer" sessions in the visitor centre at Jodrell Bank. There are several answers to this, some of which are: it's interesting, there are technological spin-offs, and it (hopefully) inspires children to develop an interest in science or engineering.
The research itself can be a bit incomprehensible to non-specialists, so public outreach relies on enthusiastic experts explaining what they do in non-technical language. As I've commented before, it wouldn't be a bad thing if the funding councils made it a condition of funding that you have to do some public outreach.
Some astronomers do this already of course (on the other hand, some hate the idea and avoid the whole public interaction thing at all costs). Last week there was a paper on astro-ph describing a project to bring science into schools using astronomy, and a collaboration between the teachers and astronomers.
The scheme consists of four visits to the school by a real astronomer during the school year. The first visit is very similar to something that the organisers of the Researchers in Residence scheme did: before meeting the researcher, they asked the kids to draw their idea of what a scientist looked like. Then the researchers come in and spend some time with the class, doing activities and explaining what they do, and then the kids are asked to draw their idea of a scientist again. The second picture is almost always dramatically different to the first. No more elderley men with strange hair, a lab coat and smoking test tubes! Progress!
Seriously, there is a lot that can be done with astronomy in schools. With a bit of imagination it can be used to cover a variety of different areas within the curriculum, something we have been trying to do with the astronomy and space Go For It for the Guides as well. If only more astronomers, and scientists in general, were willing to put in a bit of effort now and then.

Posted by Megan on Saturday 27th Aug 2005 (18:28 UTC) | Add a comment | Permalink

Sore feet!

I'm sat in a cafe in Coniston village and it is actually sunny outside at the moment. After being told by half the staff at Jodrell that I should have a holiday (ok, not quite half, but it felt like it) I took one. On Monday after getting back from Gaping Gill I packed my big rucksack and went to bed. On Tuesday I caught a train to Windermere and pitched my tent in a little campsite by the edge of Coniston Water. Tuesday night was very wet and windy, and a lot of people packed up and left the next morning. One tent ended up down the field at the bottom of a stream, and another lot (who were on the same bus as me from Windermere - one of their kids attached herself to me and kept trying to help me pitch my tent) appear to have given up and abandoned their tent altogether! Happily, my little tent (a Tadpole) stood up to the buffeting exceptionally well.
Yesterday I packed most of my stuff back in my rucksack and set off, leaving just the tent ans sleeping bag behind. Without a proper route plan I set off in the direction of Torver, vaguely intending to go up the valley and over the Old Man of Coniston. In the end I decided that the ridge looked more interesting so I walked over Brown Pike, Buck Pike and Dow Crag (on top of which I met a guy from Kendal coming the other way, why does everyone laugh when I say I'm an astronomer?!), and then up onto the Old Man itself. It was very windy, but the cairn on top of the old man is huge so I sat behind it and brewed up a mug of tea, very civilised! I also met five girls doing their Duke of Edinburgh expedition. I aksed where they were heading to and they weren't really sure "we're only on the first side of the map, I'm not sure!"
While scrambling down from the top of Dow Crag I managed to twist my ankle when a rock moved under my foot as I landed. It didn't hurt too much at the time, and I got back to the campsite without a problem, but it swelled up overnight and is now strapped up with a bandage. Typical isn't it? The first time I've ever had to use first aid, and it's on myself! Still, not to worry, it was a good walk and, although my body is complaining a bit, I feel great. Breakfast on the shore of the lake, this is the life!

Posted by Megan on Thursday 25th Aug 2005 (13:28 UTC) | Add a comment | Permalink

Gaping Gill

Gaping Gill main chamber from sand bank
Credit: Megan

Today, Mum, Keith and I went to Gaping Gill, a huge natural cavern in Yorkshire. Twice a year, caving clubs set up a winch and take the public down into the main chamber (see image, click on it for a larger version). In August the winch is run by the Craven Pothole Club. This year it is open this week, including the weekend, and it is well worth a visit. To get down in to the chamber, you sit in a metal chair which is winched down the main shaft to the floor of the main chamber. As you descend you pass very close to the rock face, and go past a ledge on one side just before it opens out into cavern. Normally there is a stream which runs down from Ingleborough, but the club divert most of it so that there is only a trickle of water accompanying you during the descent. The cavern is amazing, and the club members give guided tours explaining the history of the place. There are more than twelve miles of known passages in the system but, as visitors, you don't leave the main chamber. There is plenty to see though, and we spent a couple of hours there. It's funny, I've been to winch meets several times before, and I always seem to enjoy it more each time I go.

Posted by Megan on Monday 22nd Aug 2005 (22:28 UTC) | Add a comment | Permalink

Sundogs

A sundog seen near sunset, 21st August 2005
Credit: Megan

Here is an image of a sundog that appeared near sunset today. Sundogs, also known as parhelia, appear when light is refracted by ice crystals in the atmosphere. They are usually only seen at sunset or sunrise and, like halos, always appear at an angle of 22 degrees to the Sun. For sundogs to be visible, the ice crystals have to be in the same plane as the Sun and the observer. If the crystals are long, thin and oriented randomly then a halo is seen, if they are flat and mostly arranged horizontally then we see a sundog instead. The flat, hexagonal crystals act like tiny prisms which refract the light, splitting it into the component colours, with red appearing closest to the Sun.

The old wives tale that a halo indicates bad weather to come has some truth to it as they are caused by cirrus clouds which often indicate an approaching weather front.

There are many other phenomenon caused by ice and water vapor in the atmosphere, sometimes there are halos around the Moon, and sometimes there are Sun pillars (not to be confused with crepuscular rays) which also look quite spectacular.

Posted by Megan on Sunday 21st Aug 2005 (22:57 UTC) | 2 Comments | Permalink

The power of perl - take 2

Thanks to Stuart, and one of the longest five minute jobs ever, this is now a "proper" blog! As you can see, it lets you post comments, has an archive, and an rss feed. It also makes use of Stuart's time converter script so by hovering your mouse over any timestamp in the blog you can find out what it is in your local time zone.

Posted by Megan on Sunday 21st Aug 2005 (11:35 UTC) | 1 Comment | Permalink

Test!

Marzipan is yummy!

Posted by Megan on Saturday 20th Aug 2005 (21:17 UTC) | Add a comment | Permalink

Sunset

Sunset, 17th August 2005
Sunset, 17th August 2005

Credit: Megan

Last night's sunset was very, very red (the Moon looked pretty red too). It looked pretty spectacular behind the Lovell telescope (bottom image). While I was watching the Sun go down, I noticed that there were several engineers on the telescope structure. The duty controller (which happened to be Andy) told me that they were using jacks to raise the entire top section of the telescope: the wheel girders and the bowl itself. This is in preparation for some major engineering work to be carried out later in the year. The plan is to add additional bearings on the bottom of the bicycle wheels so the entire mass of the telescope will need to be lifted in order to install them. To make sure they know they can do this safely, and just what equipment will be necessary, the engineers were testing out the proceedure. From the ground beside the fence which surrounds the base of the telescope you couldn't see it actually move, but it is very impressive that four people with the right equipment can lift that much metal. If you look very carefully, you can see a couple of the engineers in the lower image on the left (click on it to see a larger version).

Posted by Megan on Thursday 18th Aug 2005 (18:53 UTC) | Add a comment | Permalink

Couldn't they find a real astronomer?

Along with the usual ones about black holes and planets during Ask an Astronomer in the visitor centre today, there were a few daft questions from the audience. One guy asked "Couldn't they find a real astronomer today, is that why you're here?" Later on, from the same group, a guy asked something along the lines of "I'm an Aquarius, what in store for me in September?" Very silly. Whether they wanted it or not, they got a quick description of why astrology is a load of dingos kidneys :-).

Posted by Megan on Thursday 18th Aug 2005 (15:14 UTC) | Add a comment | Permalink

Galactic cannibalism

How do galaxies form? This is one of those big questions in astronomy, no one really knows. There are plenty of theories, and many observations providing evidence for different ideas, but the truth is that we just still aren't sure.

One particular model of the universe suggests that large galaxies, like our own Milky Way, formed as an amalgamation of smaller galaxies, proto-galaxies if you like. One of the consequences of this theory is that these larger galaxies should be surrounded by a halo containing the dispersed debris left over from the mergers of these smaller dwarf galaxies. Evidence for this theory is seen within our own Galaxy.

The first dwarf galaxy remnant discovered in the Milky Way is known as the Sagittarius dwarf because it is seen in the direction of the constellation of Sagittarius. In 1994, while investigating the motions of stars in the Galactic halo, researchers discovered a large group of comoving stars, stars moving with the same speed in the same direction. It seems that this poor little galaxy is slowly being ripped apart as it passes through our Galaxy again and again. Each pass through the plane of the Galaxy causes the dwarf to become more stretched out until, eventually, it becomes absorbed into the much larger Milky Way.

Canis Major dwarf galaxy

Credit: Dr R. Ibata et al

More recently, a group of researchers have found another dwarf galaxy being torn apart by a close encounter with the Milky Way. The Canis Major dwarf is the closest known dwarf galaxy to the centre of the Milky Way, there could be others there that we haven't seen yet, and is only about 2500 light years away from our solar system. If it is so close, why hasn't it been seen before? Well, the trouble with the centre of the Galaxy is that there is a lot of stuff in the way. The bulge is full of gas, dust and stars that block out any light coming from the far side. This new galaxy was discovered by looking at infra-red data from the 2-Micron All Sky Survey which is able to penetrate this junk and reach us. Stars which appear bright at infra-red wavelengths are cooler, older stars, implying that the Canis Minor dwarf is very old. As well as finding the core of the interloper, the astronomers also found streamers of associated stars that were pulled off by tidal interactions as the galaxies got close to each other. These contribute to the disk of the Milky Way, so it seems that smaller galaxies do indeed contribute to the formation of larger ones.

Today, B. Conn and colleagues report observations of a stream of stars known as the Monoceros Ring which is tidal debris that is possibly associated with the Canis Major dwarf. This ring is behind the Canis Major dwarf and is thought to be a tidal stream from the Canis Major dwarf itself, a scenario which these new observations support. This all shows that, far from being evolved, our Galaxy is still forming as these interactions continue.

It is worth downloading the paper from astro-ph just to read the rather bizarre acknowledgements, if nothing else.

Posted by Megan on Thursday 18th Aug 2005 (13:45 UTC) | Add a comment | Permalink

How heavy is a black hole?

It depends what it had for lunch! Astronomers are fairly sure that black holes exist in the centres of most galaxies, not just large, luminous galaxies. But what are they? When a very massive star runs out of fuel and collapses, the nuclear reactions at the centre stop. These reactions produce photons which we see as heat and light, and the pressure keeps the star from collapsing under it's own gravity so when they stop, the star begins to collapse. If the star was heavy enough, the collapse continues until the core is so dense that the escape velocity becomes greater than the speed of light. As nothing can travel faster than this, nothing can escape a black hole, not even light, which is why they are known as "black" holes. The black holes in the centres of galaxies are much more massive than those formed by the collapse of stars and are known as supermassive black holes.

One method of estimating the mass of a galactic black hole is to look at the stars in orbit around it. The more massive the black hole, the faster the stars will be moving in their orbits. The speed can be measured using redshift measurements, an effect similar to the change in pitch of a siren as an abulance speeds past. In this case we are interested in the colour of the light rather than the pitch of the sound, but the idea is the same. The faster the stars go, the bigger the shift in the colour of the light from the stars. This shift can be seen as a broadening of the emission lines from the stars: the broader the line, the greater the velocity and the heavier the black hole. This only works for relatively nearby galaxies though, it gets trickier when the galaxy in whiuch you are interested is more distant.

The paper that grabbed my attention on astro-ph today described a method for estimating the mass of a black hole in the middle of a galaxy by observing emission caused by hydrogen atoms. Each atom emits at particular wavelengths (colours) depending on the energy levels of electons orbiting the nuclei. Each kind of atom has slightly different levels so by looking at the colours in a spectrum you can work out what atoms are present in a particular cloud of gas. The standard method of determining the mass of a galactic black hole is to look at the overall emission (the continuum) and the width of one particular line known as Hβ. The trouble is that Hβ can be difficult to measure. What these researchers have found is that the width of another hydrogen line, Hα, has a strong correlation with the width of Hβ. As Hα is often easier to measure, this correlation makes determining the masses of many black holes much easier.

Posted by Megan on Wednesday 17th Aug 2005 (17:59 UTC) | Add a comment | Permalink

Pulsar astrophysics

Today there is a paper on the astro-ph archive by Dave Champion and collaborators describing some of the pulsar timing they have been doing with the Arecibo radio telescope in Puerto Rico. You will have seen this telescope if you have even watched the film Contact (where Jodie Foster goes looking for alien signals) or the James Bond film GoldenEye (where it gets destroyed at the end).

What the researchers have done is use the telescope to measure the pulse profiles of a number of pulsars. Most pulsars are weak radio sources so to accurately measure the shape of the pulse profile you need to measure many of them and add the signals together. This is useful because the shape of the pulse profile can provide information on the characteristics of the emission regions on the surface of the pulsar itself, telling us about the extreme physics involved. Using the observations they measured "drifting subpulses", features in the pulse profiles that move with time. These are thought to be caused by small patches of emission, sub-beams, on the surface of the pulsar which move in and out of our line of sight and so appear to come and go.

Posted by Megan on Tuesday 16th Aug 2005 (23:33 UTC) | Add a comment | Permalink

Hardraw

Star trails at Hardraw

Credit: Megan

The village of Hardraw is pretty dark. On the Philip's Dark Sky Map of the UK it lies in a patch of blue which corresponds to a visual limiting magnitude of 5.5 to 5.75. The theoretical limiting magnitude of the average human eye under perfectly dark conditions is about magnitude 6, so Hardraw is petty good. (One of the things about astronomy is it's slightly bizarre measurements, mostly due to the fact that astronomy is such an old science. Magnitudes get larger as objects get fainter, so magnitude -27, the apparent brightness of the Sun, is brighter than magnitude 0, the apparent magnitude of a star such as Vega, which is brighter than magnitude 6.)

Malcolm, one of our members, gave me a lift up on Friday afternoon, and during the drive up the weather looked very promising. Most of the way we had clear skies and sunshine, until we got north of Lancaster and into the Yorkshire Dales National Park at which point we encountered thick grey cloud. Typical. Still, we were not too upset as we've had worse evenings turn out reasonably. Sure enough, by sunset the skies were clearing slightly and most people had set up their telescopes just in case. The sky was patchy for quite a while but that gave us plenty of opportunity to investigate the range of equipment that had been brought along. There were short-tube refractors, large schmidt-cassegrains and a few newtonians, as well as several different styles of camera.

A quadrifilar helicoidal antenna

Credit: Kevin G. Shea

My favourite was Alan's new aerial: a quadrifilar helicoidal antenna which is used to pick up weather satellite transmissions at 137 MHz. It's a beautiful-looking piece of technology, a helical structure constructed from copper piping that looked something like the image on the right.The signal is sent through a hand-held scanner, the output of which is fed into a computer using the soundcard line in as an analogue to digital converter. Some software then takes this signal and translates it into an image, similar to the way a fax machine works. When he set up for the first time we heard the satellite through the speaker on the scanner and the software appeared to be receiving data, although the picture on the screen looked rather like noise. After the satellite had passed below the horizon the data was processed a bit and we got an image. It may have been cloudy in Hardraw, but the skies were clear over Sicily!

After that, the skies cleared up nicely and we were treated to some of the best seeing conditions we have ever had. The Milky Way was easily visible rising in the east underneath Perseus, running overhead through Cassiopeia, Cygnus and Aquila, and setting behind the hills in the west. There is so little light pollution there that the Galaxy can be seen almost to the horizon. While some chose to recline in deck chairs watching for Perseids, others spent the evening hunting for faint deep sky objects. I spent most of the evening sat on the wall with my camera taking time exposures of the Galaxy, accompanied by a soundtrack composed of a baseline of whirring motors, periodic calls asking if anyone wanted to see such-and-such an object, and a chorus of "oooh!"'s and "ahhh!"'s as meteors flew overhead. The Perseids put on a good show this year. There were many faint ones, and several really bright ones that left glowing trails that persisted for several seconds in some cases. One was even seen to break up as it appeared to fall towards the roof of the hut.

Saturday dawned cloudy and wet. Making the most of being out of Manchester for a bit, I decided to go for a walk, even though the weather was gloomy. The Pennine Way runs up the track beside the hut so I headed off up Great Shunner Fell in the occasional downpour. I got to the top as the cloud descended so turned around and wandered back in the general direction of the village. As I got back, the sun made an appearance so out came the solar telescopes (you don't go on an observing weekend expecting to get any sleep!). Unfortunately the break in the weather was temporary and the clouds were back by the time we had finished dinner.

Despite the cloud, it was still a great weekend. The sky on Friday night really was one of the most spectacular sights I have seen in a long time. Rarely is the seeing that good, and for that to coincide with a night when we happen to be far from any light pollution was really, really lucky.

MAS at Hardraw, August 2005
Roll on October! Credit: Megan Disclaimer

Posted by Megan on Sunday 14th Aug 2005 (20:33 UTC) | Add a comment | Permalink

The Perseids are coming

Tonight sees the peak of the Perseid meteor shower, the visible effect of the Earth passing through the debris left behind when comet Swift-Tuttle passed through the inner solar system. The Society for Popular Astronomy (SPA) have a meteor section that observe these showers and record what they see for analysis. The best way to observe the shower is to find somewhere dark and look towards the East at an elevation of about 45 degrees, if you look directly towards the radiant (the point from which all the meteors appear from) then you will not see quite as impressive a show. If you do observe the shower you can help scientists by recording what you see. The SPA have a handy form for this purpose.

Another way to observe meteor showers is to listen to them on your radio. A meteor is just a little bit of dirt flying through the atmosphere. As these particles rush through the air they rub against molecules in the atmosphere and the friction causes them to heat up. The heat ionises atoms, separating the electons from the nuclei leaving an ionised trail behind. As the electrons recombine with the nuclei they emit a photon of light, this is what we see from the gound as a meteor trail. This ionised trail has another effect: it reflects radio waves. If you tune your radio to an empty part of the spectrum, somewhere where there is no station and all you can hear is static, then you may hear brief snatches of foreign radio transmissions as the signals bounce off these trails and get reflected back to the ground. Another way to do this is with radar.

Currently it is raining here in Manchester, but hopefully the weather will be better this evening as I am off to deepest darkest Yorkshire with some members of Macclesfield Astronomical Society.

Posted by Megan on Friday 12th Aug 2005 (01:11 UTC) | Add a comment | Permalink

MRO Delay

The launch of the Mars Reconnaissance Orbiter has been delayed 24 hours after a fault was found with a gyro unit similar to the ones used in the Atlas V rocket which will carry MRO into space. These gyro units are important as they form part of the guidance system on the rocket, essential if you want your spacecraft to end up in the right place! (Incidentally, it may be a gyro failure which ultimately puts an end to Hubble.)

Posted by Megan on Tuesday 09th Aug 2005 (23:28 UTC) | Add a comment | Permalink

Orchard on wheels

On the way home from work last night, a van covered in leaves passed me as I was cycling to the station. I thought that this was rather unusual and wondered if it might have anything to do with this lot. Turns out that they do, it was a DGV (which stands for Dancing Grass Van, obviously).

Posted by Megan on Tuesday 09th Aug 2005 (23:23 UTC) | Add a comment | Permalink

Touchdown

Credit: NASA

Discovery landed safely at Edwards AFB at 12:11:22 p.m. GMT, about half an hour after entry interface (first contact with the Earth's atmosphere), and an hour after the initial de-orbit burn. NASA TV followed the shuttle's approach using an infra red camera, we watched as the indistinct blob started to become shuttle-shaped and then turn in the final banking maneuvre before touchdown. Because the camera was infra red, you could see the temperature differences across the body of the craft, the leading edges of the wings showed up brighter than the body due to friction with the atmosphere.

Posted by Megan on Tuesday 09th Aug 2005 (13:21 UTC) | 2 Comments | Permalink

Less than one hour to go...

Discovery has now performed the de-orbit burn and is on the way back to Earth. Due to the weather in Florida, the shuttle will land at Edwards Air Force base in California at about 1215 GMT. NASA have a virtual control centre where there are regular updates on the status of the shuttle and goings on in mission control.

Posted by Megan on Tuesday 09th Aug 2005 (12:42 UTC) | Add a comment | Permalink

Discovery and MRO

Discovery was due to return to Earth today but, due to bad weather at the landing site, this has been postponed to tomorrow. Fingers crossed for a safe return to Earth for the shuttle and its crew.

Credit: NASA

This is a busy week for NASA as Wednesday will see the launch of the Mars Reconnaissance Orbiter aboard an Atlas V rocket. This probe is designed to orbit Mars at a height of around 450 km, looking for evidence of the history of water on the planet by taking close-up photographs of the surface, analysing surface rocks to look for certain minerals associated with water and examining the content of the atmosphere. The mission page has this list of science objectives:

  1. Characterize the present climate of Mars and its physical mechanisms of seasonal and interannual climate change
  2. Determine the nature of complex layered terrain on Mars and identify water-related landforms.
  3. Search for sites showing evidence of aqueous and/or hydrothermal activity.
  4. Identify and characterize sites with the highest potential for landed science and sample return by future Mars missions.
  5. Return scientific data from Mars landed craft during a relay phase.

MRO will accomplish all this using an array of science instruments: a high resolution camera, a spectrometer working in the optical and near-infrared parts of the spectrum, a "context imager" (wide-field camera), subsurface radar to look for signatures of ice below the surface, an atmospheric probe to investigate temperature, dust and water vapour variations with height, and another imager to observe clouds and watch dust storms.

MRO will transmit its data back to Earth using powerful radio transmitters which will be available for future missions to Mars. This (according to NASA) is the start of an interplanetary internet, which really means that they want to transmit lots of data. This probe will use a part of the spectrum known as the Ka-band at frequencies around 32 GHz. Most of the transmissions using the current Deep Space Network (DSN) use X-band at frequencies around 8 GHz. Ka-band is four times higher in frequency, so it can carry around four times as much information. MRO will use both as the Ka-band system is still being tested, so this mission is also an experiment in communications.

Posted by Megan on Monday 08th Aug 2005 (22:45 UTC) | Add a comment | Permalink

You're a Star

Not in the sense of fusing hydrogen nuclei to produce helium of course. A couple of people have said this to me recently, and it's a phrase I have been known to use myself on occasion. But if you were a star, what kind of star would you be? People who like extreme sports might be supergiants (live fast, die young) for example.

Posted by Megan on Monday 08th Aug 2005 (22:24 UTC) | Add a comment | Permalink

Envisat

Just now I saw Envisat for the first time! Since I first wrote the satellite tracker I've looked for it a few times, but until this evening I'd never actually spotted it. It was about magnitude 3 (according to Heavens Above) so it was pretty faint in the omni-present Mancester glow, but it was definitely there, passing from South to North, through Lyra and past Vega before passing over the roof of the house. :-)

Posted by Megan on Sunday 07th Aug 2005 (23:01 UTC) | Add a comment | Permalink

Perseids

Despite the atrocious light pollution here in Manchester, you can still see some astronomical objects. This evening Stuart and I were in the back yard and we saw the Andromeda galaxy (the nearest galaxy to the Milky Way), lots of satellites, and a Perseid! The peak of this shower is next weekend, but the shower is active over a few weeks so there is a good chance of seeing some on any night over the next two weeks, assuming the weather cooperates of course. It has been very cloudy over the last few weeks, so it was nice to see that the Universe is still there :-) Next weekend I'm going observing in deepest darkest Yorkshire with some members of Macclesfield Astronomical Society, hopefully we will have some luck with the weather...

Posted by Megan on Sunday 07th Aug 2005 (00:22 UTC) | Add a comment | Permalink

The power of perl(!)

My new computer is now pretty much up and running (including Apache which took a while to set up last night), although the old CD drive has now decided that it doesn't want to work properly any more! Grrr.

I've been experimenting with perl as well, after comments from Real LifeTM people that this is not a proper blog as there is no way to comment. All it does so far is let you choose which month to view. It's a start!

Posted by Megan on Saturday 06th Aug 2005 (00:09 UTC) | 2 Comments | Permalink

Finally...

At last, I have a working computer again. After a lot of messing around, my new shuttle system works at last. It's quite an improvement over my old desktop which was six years old when it died again a couple of weeks ago. Now that all the hardware works, I am now making backups again, and trying to make all the software work!

Posted by Megan on Thursday 04th Aug 2005 (12:13 UTC) | 2 Comments | Permalink

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