Mars Curiosity & a curious landing strategy

This weekend NASA launches its new mission to the red planet: the Mars Science Laboratory. On-board will be a new rover – Mars Curiosity – the larger and heavier successor to the massively successful Spirit and Opportunity which have been roaming around since up there 2004 (though Spirit stopped working earlier this year).

Curiosity will get to the martian surface in a new, untested, way. Instead of parachuting all the way down, it will complete its descent in a more controlled manner via a ‘sky crane’. I was looking for more details on this interesting maneuver and came across this great infographic from space.com explaining the whole process. Fingers crossed everything goes to plan!

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Moonlighting

When I’m not doing astronomy I love to read. I recently revisited Little Women, a book I remembered fondly from childhood, and was disappointed to find it to be nothing like my memory of it. My friend Mel saw my complaining on facebook and asked if I wanted to write about it for her book blog Mel’s Random Reviews. So, if you fancy a break from astronomy (and you don’t mind me ranting) check out Little (occasionally annoying, sometimes infuriating) Women‏.


Things that go bang from below

In the 1960s Cold War paranoia lead to the discovery of the most violent explosions in the Universe. Now instruments intended to study these massive cataclysms have detected signals coming from the Earth. While not the covert nuclear tests the original satellites were originally built to identify, these signals raise a whole set of questions about the physics of some of the most violent events on our planet.

At the height of the Cold War the US, concerned about the possibility of covert Soviet nuclear tests sent up a series of satellites to look for tell-tale flashes of radiation. These satellites began seeing something strange, they saw flashes. The Soviet military scientists hadn’t been working overtime, these were signals of astronomical origin. After decades of debate, it was shown that these were caused by the explosion of the most massive stars. Since then a succession of satellites have been flown to study light at the extreme end of the electromagnetic spectrum. One such instrument is the AGILE satellite, an Italian space observatory capable of surveying large chunks of the sky at once. As well as detecting distant Gamma Ray Bursts, it has also mapped events in our own Galaxy, such as the sudden brightening of the Crab Nebula in gamma rays last year. However in a strange completion of the historical circle it has also been detecting signals from the Earth.

Terrestrial Gamma-ray flashes are associated with spectacular lightning events in the upper atmosphere similar to this red Sprite. Credit:NASA

Terrestrial Gamma-ray Flashes (TGFs) are short bursts of gamma-ray radiation. These were first noticed by the Compton satellite and are associated with thunderstorms. Strong updrafts in clouds cause the formation of layers of positive and negative charge. There are typically eased by lightning strikes removing the net charge from one or more layers. However the strong electric fields in the clouds can accelerate electrons to velocities close to the speed of light. When a fast moving electron such as this (or from a source such as a cosmic ray) interacts with another electron it can accelerate it too leading to a run-away growth of fast-moving electrons. These are then diverted by interactions with atomic nuclei in the cloud releasing “braking radiation”. As the electrons are moving so fast, this radiation takes the form of extremely energetic gamma-rays.

As the AGILE satellite passes along its orbit it is capable of detecting TGFs from below. However an orbital inclination of 2.5 degrees limits the area where the satellite can detect these flashes to close to the equator. Happily this is where some of the Earth’s largest thunderstorms happen. From June 2008 to January 2010, AGILE scientists isolated over a hundred TGFs detections. The largest number of detected events came from Africa with others being found over Indonesia and a few over South America. However when it came to associating these events with lightning events they found something striking (excuse the pun). At first glance it appeared that the distributions of Terrestrial Gamma-Ray Flashes and lightning matched rather well. But when the distributions were studied in more detail, it was found that while in South America there was an 87% chance that that TGFs came from a random sub-sampling of lightning, this probability dropped to 3% in Africa. The authors don’t go on to explain this discrepancy, but it is clear there is still something unknown about the mechanisms driving some of the most violent events on the planet.

Source
AGILE Observations of Terrestrial Gamma-Ray Flashes , M. Marisaldi et al., 2011 Fermi Symposium proceedings


How to (hopefully) not drown in data

More is better, right? Bigger telescopes and bigger surveys are both undoubtedly good things, but to make the best use of these advances we need to be able to handle the corresponding increase in data flow, and subsequent pressure on the astronomical archives which are going to have to cope with it.

This is a cross posting with the Astronomy Twitter Journal Club who are going to be discussing this topic on twitter (search for the #astrojc hashtag) this Thursday at 20:10 GMT. If you’re interested please come and join in.

This ‘data tsunami’ is almost upon us, according to a new paper by G. Bruce Berriman and Steven Groom. The recent addition of large datasets from the Spitzer and WISE telescopes has massively increased queries to the online Infrared Science Archive (IRSA), and, unsurprisingly, slowed down the response time of the database. This is only going to get worse as the archive’s growth is expected to accelerate over the next few years.

The paper also points out that how astronomers use archives is going to change. At the moment, raw datasets are typically downloaded and then reduced on a user’s own computer. However, once data reach peta-byte scales it’s likely that they’ll have to be handled in situ, if only to avoid breaking the internet.

So what can be done? And, more importantly, can we do whatever we’re going to do in as cheap a way as possible? Firstly, we need better ways to search multiple online datasets efficiently – the excellent Virtual Observatory is already developing techniques to help here.

Next, we need to explore new technologies like cloud computing. The Square Kilometre Array (which will generate 10 gigabytes per second) will have theSkyNet, the (worryingly named) community based cloud which will harness the power of volunteers’ computers to process its data.

Finally we need to talk more, especially to IT experts in computer infrastructure, and then share what we’ve learned in the authors’ proposed new journal dedicated to information technology in astronomy. We then need to properly reward the effort people put into this area, as well as giving young astronomers a grounding in software engineering to better prepare them for this data-heavy future.

If we do all that then, the authors’ suggest, we’ll be able to survive the coming data flood. Fingers crossed.

ResearchBlogging.orgG. Bruce Berriman, & Steven L. Groom (2011). How Will Astronomy Archives Survive The Data Tsunami? ACM Queue arXiv: 1111.0075v1


Backstage science – the telescope with 24 eyes

KMOS, the K-band Multi-Object Spectrometer, is a huge instrument for a Very Large Telescope in Chile. It’s currently being built and tested at the Astronomy Technology Centre in Edinbugh by, amongst others, my friend Michele. I’ll let him tell you all about it: