Posts Tagged ‘Herschel’

Tracking Planck and Herschel

May 21, 2009

As well as the official ESA ground stations which are tracking Planck and Herschel, a group of (mainly) Spanish astronomers have been observing them with optical telescopes.  They’ve also identified a few other pieces of the Ariane 5 upper stage travelling along with them, as well as the Sylda adapter which separated them within the rocket fairing.

Optical observations of Planck, Herschel and the Sylda adapter

Optical observations of Planck, Herschel and the Sylda adapter

On their “Images” page, you can see some light curves – which show how the brightness of the objects varies with time – for Herschel, Planck, Sylda, and a few other fragments.  The vertical axis, labelled “R”, is the brightness in astronomical units of “magnitudes“.  For comparison, the faintest stars visible with the naked eye are around magnitude 6, and a higher number means fainter – I’m sure this made sense to Ptolemy and Hipparchus.  In fact, the scale is logarithmic, so a magnitude of 17 is about 10,000 Ifainter than magnitude 6, putting them at around the same brightness as a small asteroid or a larger Kuiper Belt Object.

Light curves of Herschel, Planck and a few other fragments

It’s interesting to see that Herschel brightens by about 2.5 magnitudes (about a factor of 10) at one point.  There is one very plausible explanation for this: the timing coincides pretty much with the orbital manoeuvre which Herschel executed on 18th May, which must have oriented the solar panels to a more favourable angle for reflecting sunlight back to Earth.  Planck and the other fragments show smooth gradual declines in brightness over time as they get further from Earth.

So here’s where I make a prediction, just as any scientist should.  I predict that Sylda and the fragments will eventually fall back to Earth and burn up, so they might brighten a little.  They’re almost certainly in elliptical orbits so may vary slightly as their distance from Earth changes, and also if they’re spinning or tumbling at all. [I've been corrected by Bill Gray (see comment), who informs us that Sylda and the fragments will end up in heliocentric orbits - i.e. orbiting the Sun]. Planck’s brightness should stabilise when it reaches its final orbit around L2, as its angle realtive to the Earth and Sun should stay pretty much constant.  I predict that Herschel, however, will show slight variations in brightness as it slews to point at various objects around the sky – though it has to keep its solar panels pointed somewhere towards the Sun.  Whether the variations will be large enough to observe with telescopes on Earth remains to be seen.

If you want to see how far Planck and Herschel are from Earth, then you can use the JPL Horizons catalogue.  It’s somewhat self explanatory, but the output can look a little technical.  Change the “Target Body” and search for “Herschel” or “Planck”.  You also have to make sure that the time span covers the range you want.  For teh table output, I recommend selecting “Obsrv range and rng rate” and “One-Way Light-Time” – though there are many to choose from (though not all applicable).  You can set some of the units in the “optional” section.  When you hit “Generate ephemeris” you’ll get a table showing the numbers you’ve requested, and even a table explaining what they all mean.  There are a few options if you want to export the results to a file your favourite spreadsheet programme can read, so you can make your own plots.  You can play with a few other things too, such as setting the observer location to L2 (by putting “@392″ in the “Lookup Named Location” box).  It’s not certain that the orbital parameters used are exactly what Planck and Herschel will actually use, but they’re probably not too far off.

On their “Images” page, you can see some light curves – which show how the brightness of the objects varies with time – for Herschel, Planck, Sylda, and a few other fragments.  The vertical axis, labelled “R”, is the brightness in astronomical units of “magnitudes“.  For comparison, the faintest stars visible with the naked eye are around magnitude 6, and a higher number means fainter – I’m sure this made sense to Ptolemy and Hipparchus.  In fact, the scale is logarithmic, so a magnitude of 17 is about 10,000 Ifainter than magnitude 6, putting them at around the same brightness as a small asteroid or a larger Kuiper Belt Object.

Planck and Herschel as seen from the ground

May 20, 2009

As they started on their way to L2, the Planck and Herschel satellites were observed from Earth.  The ESA “Optical Ground Station” on Tenerife, which is one of the stations that tracks ESA satellites and monitors their progress, observed them a few hours after launch and made this animation.  At this time – around 21:30 GMT on 14 May 2009, just over 8 hours after launch – they were 100,000 km from Earth.  That’s already a quarter of the distance to the Moon, but only around 1/15th of their final distance from Earth – L2 is 1,500,000 km from Earth.  They were also seen by the Faulkes Telescope in Australia.  In both images, there are 3 moving dots.  The two brighter ones are Herschel and Planck while the fainter one, which is quite close to Planck, is the SYLDA 5 fairing which separated the two spacecraft in the rocket.

Soon the spacecraft will be much, much further away, and much more difficult (if not impossible) to see – at a few metres across they’re right on the lower limit of the smallest near-Earth objects observed.  Their brightness will primarily be due to the reflectivity of the solar panels.  Since these are pointed towards the Sun, and therefore almost at Earth, it might work out now and again as Herschel and Planck move in their orbits.  I haven’t crunched the numbers to work out if this is possible (exercise for the reader?), but it should certainly be a challenge.

Launch!

May 14, 2009

Cross-posted on Andrew Jaffe’s Blog and the Planck Mission Blog.

Planck and Herschel are en route to their orbit at L2!

We were about 7.5 km from the launch, at the “Agami” viewing site. Here is my golden ticket:
Planck launch badge

We all milled around for half an hour, snapping pictures of friends, eminent scientists, and at least one Nobel prize winner, but it all went silent when they announced the last few minutes before launch. The inevitable 10.9.8.7.6.5.4.3.2.1 and ignition was followed by a still, silent seven or so seconds, and then we saw the smoke and flames.
Herschel/Planck Liftoff
(Apologies for the poor quality; there were many people there with far more powerful zoom lenses than my meagre 2.5x.)

The rocket then pierced the clouds:
Herschel/Planck in the sky
Soon after, the booster rockets separated (which those 200x telephoto lenses could capture), and soon all left to see with the naked eye was the rocket’s trail:
Herschel/Planck contrail

For the rest, we had to watch the video feed from the control room, and, about half an hour later we finally heard what we were waiting for: first Herschel, and then Planck, had separated from the rocket and were on their own, off to L2. Four or five hours later, Planck’s instruments had been turned on, and the ESA team in Darmstadt was monitoring their progress. There’s a lot going on now, but we won’t have anything like scientific data for two or three months — and then our work is cut out for us.

Huge thanks to the instrument teams for their hard work for more than the last decade. Soon, the hard part for us scientists and data-analysts begins: four or so years of data coming down from the satellite, being cleaned and calibrated, building and rebuilding our (computer) model of the instrument, letting us build and rebuild our models of the Universe.

Thanks also to the HFI Instrument Principle Investigator and co-PI, Jean-Loup Puget and Francois Bouchet (and especially Hélène Blavot) for arranging this extraordinary opportunity for us scientists to see this part of the fruits of our work.

Launch Blog — Day 2: Rollout

May 14, 2009

Cross-posted on Andrew Jaffe’s Blog and the Planck Mission Blog.

Today we saw the rollout of the gargantuan Planck/Herschel Ariane 5 rocket, when they move it from its assembly building to the launchpad. Spectacular!
Planck Rollout
There are plenty more pictures, and some movies, which I’ll try to edit and post shortly. At the end of the day, I was interviewed and inadvertently kidnapped by Chris Lintott and the BBC Sky at Night team. But I am here to tell the tale (and better fed for it) and ready for the — very — big day tomorrow.

Live coverage of the launch, scheduled for 2:13pm on 14 May, at:

Pre-launch blitz

May 8, 2009

Cross-posted from Andrew Jaffe’s Blog:

With less than a week to go before its planned launch, The Planck Surveyor Satellite has been loaded into the fairing of its Ariane 5 rocket along with its sister satellite, Herschel. It is scheduled to be rolled out to the pad on May 13, and the launch window opens on May 14 at 13:12 GMT. Within three months, it will be at the Lagrange 2 (L2) point, from where it can watch the sky with the Sun, Earth and Moon all comfortably shielded from view.

Once there, Planck will scan the sky for at least 14 months. But don’t expect to see much out of the mouths (or blogs, or printers) of Planck scientists for a while: we’ve got a full year thereafter to analyze the data, followed by a year’s “proprietary period” during which we’ll do our best to extract the most exciting science. But until then — the first rule of Planck is: you do not talk about Planck. The second rule of Planck is: you DO NOT talk about Planck. (Luckily, Herschel expects to release its pictures of the infrared and submillimetre universe much more quickly.)

For now, the European Space Agency, the UK’s Science and Technology Facilities Council, and of course us Planck scientists ourselves have been gearing up both for the scientific data — and the press.

ESA has a Herschel and Planck launch campaign page with a nifty live countdown (which users of Apple’s Safari browser can make a dashboard widget out of). Last week, STFC held a pre-launch press event in London, which got us some coverage in The Independent, The Daily Mail, The Telegraph, The Times, as well as BBC Radio and TV news. (And Sky at Night will have coverage from the launch.)
We’ve also been covered in New Scientist (complete with always-exciting quotes from me).

If this media saturation isn’t enough, you can check out the page dedicated to Planck in the UK, Follow Planck on Twitter (and Herschel too), read the Planck Mission Blog (there’s one for Herschel, too).

As for me, I’m taking a break from this term’s teaching — off to French Guiana next week for the launch (barring further delays). For those of you less lucky, it will be visible on satellite tv and streamed by ESA. I’ll do my best to keep up the twittering and blogging, probably cross-posting from here to the Planck Mission Blog. Wish us luck!


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