Space probe or Satellite?

In my day job, I work on instrumentation for a telescope that will be launched into space early next year. Throughout the time I've been working on it I've always had a nagging thought at the back of my mind. Am I working on a satellite or a space probe?

I assume this isn't a question that too many people think about, even in the space community. The International Space Station, the Hubble Space Telescope and geosynchronous satellites are all, well, satellites of the Earth whereas New Horizons is a space probe on its way to Pluto and beyond. Venus Express, Mars Express and Cassini-Huygens were space probes which have now become satellites of Venus, Mars and Saturn. All very straightforward, so why don't I know which I work on?

My telescope, along with several other missions, will be heading to a special place in space named L2. L2 is one of five Lagrangian points - a point where the gravitational forces of the Earth and Sun balance each other - and is located 1.5 million km away from the Earth in the direction opposite to the Sun. As for Goldilocks, things have to be just right at a Lagrangian point. Just a bit further away from L2 and you would be left behind by the Earth in your orbit around the Sun. Just a little closer and you would orbit the Earth more than once per year. At L2 the Earth gives you just the right amount of a tug to keep you orbiting both the Earth and the Sun exactly once per year. The result is that you always appear to stay in the same place relative to the line joining the Earth and Sun.

L1 and L2 mark the extent of the Hill Sphere of the Earth. As the Bad Astronomer points out, objects within this sphere, such as the Moon, can be considered to be a satellite of Earth. As Planck will sit on the edge of that sphere, and thus on the very edge of interplanetary space, that makes it almost a space probe and only just a satellite.

Perhaps I'll just stick to calling it a spacecraft.

Posted in astro blog by Stuart on Monday 29th Sep 2008 (19:08 BST) | Permalink

Join the Wait

There are few times you hear about a revolution in our approach to a problem. For years great people have been searching for extra-terrestrial intelligence (SETI) but now the WETI institute are taking a different approach. Rather than spend millions of pounds or dollars actively searching for extra-terrestrial intelligence, why not just wait for it to come and find us. This approach is much more cost effective than many projects in astronomy and is an awful lot easier too. You can even download their WETI@Home software which, given enough participation, will allow hundreds of years worth of waiting to be done in a matter of days.

The WETI institute have a poster on display at the .Astronomy conference in Cardiff and I'm going to ask them to put this brilliant piece of work online. I have the pin badge, I've read the poster, and now I'll sit back for a cup of tea and wait.

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Posted in astro blog by Stuart on Tuesday 23rd Sep 2008 (10:53 BST) | Permalink

2009 MoonWatch

One of the cornerstone projects for the International Year of Astronomy (IYA) is named 100 Hours of Astronomy. The plan is to organise astronomical observing events all over the world over a period of 100 hours. This should be a cool global event.

Ian Robson - head of IYA2009 in the UK - has been talking about IYA at the .Astronomy meeting this morning. As well as showing the great IYA2009 trailer, he points out that in the UK we don't really have much chance that we'll get 100 hours of clear sky just when needed. To get around our rather unpredictable weather, the UK IYA team are spreading our chances of good weather by having two MoonWatch weeks. One will be in the spring (March 28th - April 5th 2009) and one in the autumn (October 24th - November 1st 2009).

Ian didn't mention if Bill Oddie and Kate Humble are going to be involved.

Posted in astro blog by Stuart on Tuesday 23rd Sep 2008 (09:39 BST) | Permalink

.Astronomy begins

As UK astronomy bloggers probably know - because several of them are here - I'm in Cardiff visiting the .Astronomy conference. The conference is great for me because it brings together two areas I'm interested in; astronomy and new media (web stuff). That means plenty of interesting talks covering Galaxy Zoo, the Faulkes Telescope, AstroGrid, the Virtual Observatory and much much more. The talks are available live via ustream for those who can't be here in person. Rob is also twittering with comments and links that are mentioned during the talks.

The first session happened this morning and was about Citizen Science; projects where anyone can take part in doing real science. This morning Chris Lintott announced the imminent launch of Galaxy Zoo 2 to build on the efforts of the 165000 users who have helped sort 900000 galaxies in the Sloan Digital Sky Survey (SDSS). Zoo 2 sounds pretty exciting but I was more intrigued by Chris's announcement of a future "Universe Zoo" (or "Zooniverse" - they haven't yet chosen a name) which will allow people to analyse data other than the SDSS. There are some interesting ideas in Universe Zoo including creating a guide book of the Moon using data from NASA's Lunar Reconnaissance Orbiter.

You may hear about the goings on over the next few days on Chris Lintott's Universe, Orbiting Frog, the Daily Ack, the e-Astronomer or even here on Astronomy Blog.

Posted in astro blog by Stuart on Monday 22nd Sep 2008 (14:30 BST) | Permalink

LHCb Logbooks

As everyone has realised, the world didn't end today. Great! Now lots of very clever particle physicists can get on with analysing the data they have started to acquire at the Large Hadron Collider.

One of the groups working on the LHC is the LHC Beauty Experiment (LHCb). This isn't a particle physicists "Am I Hot or Not" but an experiment to get precise measurements of CP

violation and rare decays (complicated particle physics). Like any good experimentalists they are keeping log books to record what they're doing. In fact, their log books are available online for everyone to see. I think this is very cool. Of course, I haven't a clue what most of the log entries are talking about as they are using the local jargon, but it is cool to see plots showing the passage of the beam through LHCb. The logs also show that the operators have a sense of humour.

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Posted in astro blog by Stuart on Wednesday 10th Sep 2008 (22:44 BST) | Permalink

The Day After Tomorrow

As I'm sure everyone must be aware by now, on the day after tomorrow the Large Hadron Collider will have its first circulating beam of protons.

The LHC is based at CERN - birth place of the world wide web - and has involved a huge number of scientists from a huge range of countries working for many years to construct. It marks the next step in the ability of particle physicists to test the "standard model" of particle physics. The standard model is just the idea that everything is made up of six quarks (up, down, top, bottom, strange and charm), six leptons (mu, tau and electron neutrinos and their anti versions) and the four known force carriers (the wonderfully named bosons).

Wednesday will be a landmark in getting the LHC up to its full energies but it still won't be up to maximum. The press release says that the injection energy will be 450 GeV on Wednesday. For those that haven't a clue what an electron Volt is, 450 GeV is equivalent to about 0.00000007 Joules of energy. The target energy for 2008 is 5 TeV; 11 times the initial energy on Wednesday.

These amounts of energy are impressive for sub atomic particle collisions in the laboratory but not by nature's standards. People tend to forget that nature produces some stupendously high energy particle collisions in our atmosphere. The LHC will be wimpy by those energies but gives us a really fancy, top-of-the-range 'camera' all ready to record the few really interesting collisions that will help to test the standard model and show if the Higgs Boson actually exists. I can't wait for the results but they'll take a while to emerge.

To keep up-to-date you can check out the CERN site and the CERN twitter feed. Meanwhile, I'll just add some Particle Zoo plush toys to my wish list.

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Posted in astro blog by Stuart on Monday 08th Sep 2008 (23:31 BST) | Permalink

Fingerprints of Weather

The weather in Manchester feels autumnal. There has been almost constant drizzle all week accompanied by driving wind and even some leaves falling from the trees. The weather has certainly not been conducive to astronomical observations and has made my daily cycle to work and back rather damp. I did catch a very brief glimpse of what I think was Jupiter a few nights ago but haven't seen much else since.

Thankfully clouds don't affect radio telescopes too much although water vapour in our atmosphere does emit (and absorb) electromagnetic radiation in the radio part of the spectrum. If the observing frequency gets high enough, or if there is enough water vapour, you'll start to get 'clouded out' on radio telescopes too. It is also possible to 'see' storms with a radio telescope because lightning tends to emit across the electromagnetic spectrum.

Radio telescope voltages
Raw voltage levels from three radio telescopes that are part of MERLIN in the UK. CREDIT: Stuart/Jodrell Bank Centre for Astrophysics
I created a quick and dirty visualisation of some of the effects of today's weather on the raw output from three radio telescopes operated by Jodrell Bank Centre for Astrophysics. Each of the three horizontal strips represent an hour or so of readings for a particular telescope. In each case, red represents 'brighter' radio emission and blue 'fainter' emission (you can also think of it as hot and cold) but note that the scale is different for each telescope. Sudden increases in emission - spikes - can be seen as narrow bands of colour (mostly orange or red).

The top telescope in my plot is based near Cambridge and was parked i.e. it was pointing upwards and not looking at anything in particular. Whilst the banding may just be an over amplification of noise, the weather forecast has shown the Cambridge area under a heavy band of rain today. More interesting to me are the bottom two bands. These are the Lovell Telescope and Mark II telescope at Jodrell Bank Observatory in Cheshire. What is interesting is that they have common spikes. Both telescopes were observing different objects in different parts of the sky but as the spikes are in common, they must be of local origin. My guess would be that they are due to nearby lightning and the overall change from blue to green, as you go from right to left, indicates increasing water in the sky above Jodrell Bank. It looks like it was a wet evening in Cheshire.

Posted in astro blog by Stuart on Saturday 06th Sep 2008 (23:05 BST) | Permalink

Other People's Data

Taking other people's data and ideas and building upon them is what makes the sciences work. Unlike some areas of human endeavour, using other people's data is generally seen as a positive thing which benefits both parties. Just look at the academic success of the Sloan Digital Sky Survey team or the massively cited WMAP team who have provided easy access to their excellent catalogues. The reason the community are happy with this derivative work is because the original author benefits through a reputation built on citation; the people using the data will reference the origin and that helps the academic career of the original author.

The norms of scientific life mean that this system works, most of the time, but there are cases on the edges of what is deemed acceptable or ethical. This week Andrew Jaffe blogged about stealing scientific data with reference to a case where people had taken a photo of a slide of unpublished data during a conference talk and then extracted the data from the photograph. This sounds like a case of industrial espionage but it turns out that they did have permission from the original experiment's spokesperson so isn't as it first appeared. As Chris Lintott points out, putting your data in conference proceedings, in the arXiv, or having people discuss them is a form of publication. Although not peer reviewed, the buzz surrounding the unpublished data could well mean that they receive plenty of citations once they are published formally.

There are some other cases where the people making use of other people's data do not cite the original work and claim the credit for themselves. One example of this in the past few years is a case of spying on somebody else's observing logs and scooping them to the discovery of a Kuiper Belt object. That sort of behaviour is underhand and unfair on those putting in all the effort to acquire and process the original data. Although these cases are probably quite rare, I am becoming more aware of the issues.

One of my astronomical friends has been working extremely hard for a couple of years on a huge survey of the galactic plane. His team have taken hundreds of hours of observations, using a big telescope, specifically for this project. As is usual on big telescopes, they had an agreed proprietary period with which they could analyse the gigabytes of data before they became free to all. This proprietary period lets those who put effort into getting the observations made exploit them and publish their results first. The period can be anything from 6 months up to about 2 years depending on the telescope. Unfortunately, in my friend's case the data were accidentally released early and without warning. A rival group took the data, did a fairly quick and dirty analysis of it and then published them as their own.

As you may imagine, my friend isn't happy. He has agonised long and hard over those data to tease out as many systematic uncertainties and calibration errors as he can. The rival team have just done a fairly quick analysis and then taken all the credit. Will this theft of credit from my friend mean a reduction in citations for his work when he publishes it. I really hope not but if it does, that could hurt his career. I don't think my friend's case is typical but it does serve as a reminder of the impacts of unscrupulous researchers on other's lives.

Is there a moral to this? Yes. Always give credit to those whose work you use. To give them credit doesn't cost anything, it benefits them and is the right thing to do.

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Posted in astro blog by Stuart on Thursday 04th Sep 2008 (13:45 BST) | Permalink

A Bug of Fire and Ice

NGC 6302
The Bug Nebula, NGC 6302, imaged by WFPC2 on the Hubble Space Telescope CREDIT: ESA/NASA and Albert Zijlstra (JBCA).
There is no doubt that modern telescopes produce some spectacular images of astronomical objects. I saw this glorious image of the Bug Nebula (NGC 6302) for the first time today and it looked just like a painting.

Thewhite/blue filaments reaching down from the central star and the orange/red colours remind me of The Ancient of Days by William Blake. The colours and texture also evoke a dramatic Turner sunset. That second comparison is probably quite appropriate as this spacescape shows the later stages of an extremely hot star that has blown off its outer layers to form a nebula of compressed gas, dust and hailstones.

The false-colour image was created using two observations with the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope. One observation looked at the light from hydrogen (the blue in the image) and the other looked at light from ionized nitrogen (the red parts of the image).

Posted in astro blog by Stuart on Wednesday 03rd Sep 2008 (20:51 BST) | Permalink
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