Interview with a new Oskar Klein Fellow
Elena Moretti is the first of the about 300 applicants who was selected to become an Oskar Klein Fellow this year. She comes from a little country-side town, called Cartura, on the south of Padua in Italy, where she graduated in physics in 2006. She got her PhD in Trieste where she worked with the AGILE and Fermi experiments on GRBs. She developed a method that was used to calculate the flux upper limits on the GRB emission that was used in both experiments. In 2010 she moved to Stockholm working as a postdoc at the KTH. We ask her to tell us more about herself and the work she will be doing at the Oskar Klein Centre.
Congratulations Elena! You have been offered an Oskar Klein Fellowship. How does it feel?
It feels good! It gives me the opportunity to develop my newborn interest in the polarimetry field. Wen I came here 2 years ago I was working only in the high energy astrophysics field with the 2 gamma-ray experiments Fermi and AGILE. After one year a new interest was tickling me: PoGOLite. I started to work on it as a “side job” on my spare time….well I guess that would change soon.
Read more…
PoGOLite flight cut short
The PoGOLite flight did not turn out as we had hoped. A few hours after the spectacular launch at 2 AM on Thursday 7th July it became clear that the balloon’s altitude was lower than expected. It was soon after determined that the balloon was in fact leaking and that the altitude had started to steadily decrease. Since the balloon was approaching a mountainous region it was decided to terminate the flight - a 5 day flight to Canada was no longer an option. We were, of course, extremely disappointed and frustrated. During our few hours aloft we managed to commission the polarimeter and start pointing exercises with the attitude control system. The first guide stars we selected appeared nicely centred in our field-of-view and we were eagerly awaiting the Crab rising in a couple of hours time.
The first data download from the polarimeter. Happy faces!
Before shutting down the instrument we did manage to point at Cygnus X-1 and take some data. The pointing worked beautifully, but we were already too low to allow meaningful X-ray observations. The gondola was finally cut from the balloon around 0730 on Thursday morning in the vicinity of Kebnekaise and landed by parachute near to Nikkaluokta. Initial GPS information indicated that it had splashed down in a lake, but fortunately this was not the case. We managed to locate the gondola the day after and were relieved to find it relatively intact.
PoGOLite after flight termination.
So, what happens now? The first step is to understand the status of the polarimeter, attitude control system, star trackers and electronic control systems. Today we have made an initial appraisal and first results are promising. It will take more time to form a proper understanding of the situation however.
Given the excellent performance we experienced during our few hours aloft, we are keen to fly again as soon as possible!
PoGOLite launched!
At 01:57 on Thursday 7th July 2011, PoGOLite was successfully launched from Esrange. It was a beautiful sight. About an hour after the launch we are now at an altitude of 20000 metres and climbing steadily. We have activated the polarimeter and all is OK. So far, so good… We are now working through our in-flight check-lists and will soon start to position the gondola for first observations of the Crab.
PoGOLite is launched!
PoGOLite countdown has started
After a weather briefing this morning, it was decided to start the PoGOLite countdown. We currently foresee a launch around 2230-2300. Preflight tests are on-going and all is OK. We will move to the launch position in an hour or so.
So far, so good!
PoGOLite being prepared for launch.
The countdown approaches…
POGOLite is almost ready for launch! As you can see from the photograph, the polarimeter, which once filled our lab at AlbaNova, is now dwarfed by the protective gondola and solar cell arrays. The picture was taken just before Midsummer, during a launch rehearsal. This provided us with a realistic environment to tune-up our pre-flight checklists and confirm that we can operate the polarimeter, pointing system and our satellite communication systems together with the other balloon systems.
PoGOLite hanging on the Hercules launch vehicle
There are a few items remaining on our ‘to do‘ list and then we’re ready to launch. How long we need to wait will depend on the weather. There are very strict requirements placed on wind speeds at the ground and at altitudes of a few hundred metres. The countdown itself takes about 24 hours once a positive weather prognosis is received. The polyethylene balloon is unpacked at the last moment. Being about as thick as a standard sandwich bag, once unpacked it so fragile that it must either be used or thrown away.
For the latest news updates, you might like to take a look at our recently overhauled web-page.
I’ll post an update here after the launch.
An update from above the Arctic Circle
In a little over two weeks, just after Midsummer, the launch window for PoGOLite will open. In my last post, I talked about the conclusion of PoGOLite tests at Linköping airport. Since then, PoGOLite has been moved up to the Esrange Space Centre thereby marking the start of the launch campaign. Esrange is located some 40 km east of Kiruna and provides unique opportunities to launch large helium-filled balloons into the stratosphere. We are hoping to make a circumpolar navigation of the North Pole, overflying Norway, Iceland, Greenland, Canada and Russia before landing back in Sweden some 20 days later. Such a long flight will allow repeated observations of our primary science targets, the Crab and Cygnus X-1 and plenty of time to study backgrounds – which is essential for a counting rate anisotropy measurement such as polarisation. Obtaining permission to fly over Russia is a complicated business and we are still on tenterhooks waiting for the green light. If this is not forthcoming, we’ll have to cut the balloon down over Western Canada and strike out into the wilderness to recover the payload and, in particular, the valuable cargo of hard disks.
PoGOLite arrives at Esrange.
There is a lot of activity at Esrange right now with several large balloons being prepared for launch. First up are three NASA-sponsored payloads. The first two, AESOP and LEE, have flown many times before in their quest to monitor the effect of solar modulation on low energy cosmic rays. The relatively high latitude of Esrange means that cosmic rays are not screened by the Earth’s magnetic field. LEE (Low Energy Electrons), has already been launched and landed in Western Canada after 5 days. AESOP (Anti-Electron Sub Orbital Payload) will be launched as soon as weather conditions allow. The final payload in the queue is called Highwind and uses a Fabry-Perot interferometer to probe the upper atmosphere. Interestingly, LEE and AESOP have connections to my ‘other’ experiment PAMELA. You may recall that the low energy part of the well-known PAMELA positron fraction did not agree with the majority of other published balloon-borne data since these measurements were taken during a different solar configuration (polarity and activity). Measurements from AESOP collected around the time PAMELA was launched agreed with the PAMELA observations, however.
Integrating the polarimeter with part of the gondola.
PoGOLite rounds off the summer launch programme for large balloons, with the late date chosen to maximise the angle between the Sun and the Crab. So, how large is large? Well, the balloon which will lift PoGOLite to an altitude of 40 km has a volume of a little over 1 million cubic metres – about twice the volume of the Globen Arena. Such a large balloon is needed since PoGOLite is, in reality, not so light and weighs in at about 2 metric Tonnes.
An exciting few weeks lie ahead at Esrange. On-ground tests of the polarimeter continue, with a polarised radioactive source replacing photons from the Crab. The attitude control system which keeps the polarimeter aligned to targets of interest is also being put through its paces. As PoGOLite drifts Westward, Esrange will eventually drop below the horizon and the only way to contact the balloon is through Iridium satellite links. This requires that the payload can operate autonomously, rather like a satellite. Not always so easy to test realistically on the ground!
For more details about PoGOLite, you may wish to take a look at a paper which was presented a couple of weeks ago at the 20th ESA Symposium on European Rocket & Balloon Programmes (arXiv:1106.1322).
Goodbye Linköping. Hello Kiruna!
Testing PoGOLite at Linköping airport.
During the last couple of months, a large wooden structure has been puzzling passers-by at Linköping airport. Hanging from the structure is PoGOLite - a X-ray telescope which is specifically designed to determine the polarisation of incoming photons. This capability makes PoGOLite unique.
The systems which allow PoGOLite to be accurately pointed on the sky have been put their paces in Linköping. The tests finish this weekend, paving the way for a move to the Esrange Space Centre near Kiruna where a million cubic metre helium-filled balloon will lift PoGOLite to an altitude of 40 km. The ballon launch is foreseen for late June Read more…
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What is dark energy? What and where is the dark matter? What physics lies behind the most energetic processes in the Universe such as supernovae, gamma-ray bursts and black holes?
