Target comet spotted

08/06/2011

Updating Comets

Rosetta spies Comet Churyumov-Gerasimenko

The European Space Agency’s Rosetta spacecraft, launched in 2004, has just gone into hibernation until 2014, as it continues to cruise towards its far-flung rendezvous with a comet. Once there it will drop a lander on the nucleus and then accompany the comet as it orbits towards the Sun. Before Rosetta went to sleep, its camera OSIRIS was able to pick out its target, Comet Churyumov-Gerasimenko,160 million kilometres away among the background stars. This is the picture released today from the Max Planck Institute for Solar System Research (MPS).

Caption: Seen in the second enlargement from the crowded starfield of the Scorpius constellation, the comet became visible as a single point of light to the 10-cm OSIRIS telescope on Rosetta, thanks to exposures totalling 13 hours. Credits: ESA 2011 MPS for OSIRIS-Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.

We had not expected to be able to create first images from so far away,” says the lead investigator for OSIRIS, Holger Sierks of MPS.

The press release from MPS is here http://www.mps.mpg.de/en/aktuelles/pressenotizen/pressenotiz_20110608.html

And from ESA here http://www.esa.int/esaSC/SEM38RJ4LOG_index_0.html

By the way, next week (15 June) I’ll be taking part in an ESA TV programme about Rosetta and its predecessor Giotto, at ESOC, ESA’s mission control in Darmstadt.

Added 12 June: The event will start in the afternoon at 16:30 CEST. (15:30 BST) and will be webstreamed live at www.esa.int

 

 

 

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Planck’s whole sky

05/07/2010

Pick of the pics

Planck’s first overview of the cosmos

Credit: ESA / LFI and HFI Consortia

Microwaves from the entire sky, surveyed by Europe’s Planck spacecraft since August 2009, are here mapped in galactic coordinates. The centre of the Milky Way Galaxy, in Sagittarius, is in the middle. The ribbon of the Milky Way (the flat disc of the Galaxy) extends horizontally across the map, with Cygnus conspicuous towards the left and Orion towards the right. Streamers above and below the disc are regions of star formation. The more subtle mottled regions top and bottom show the cosmic microwave background, from the formation of the first atoms 400,000 years after the Big Bang. The strong microwaves from the Galaxy will have to be gauged and subtracted to reveal hidden parts of that background. Crucial for making the distinction is Planck’s range of nine different microwave frequencies, 30 to 850 Ghz, and its ability to measure the temperature of the sky to one-sixth of a degree.

In Magic Universe I call it “looking for the pattern on the cosmic wallpaper”. Named after the quantum theory pioneer, Planck is the successor to NASA’s WMAP mission. In 2003 WMAP returned wonderful information about the cosmic microwave background but did not quite pin down the theory of the Big Bang that best fits the facts. Maybe Planck will do that, and there seems little point in updating Magic Universe about the cosmic wallpaper until the full Planck results are in, after four surveys of the whole sky, in 2012.

George Efstathiou of Cambridge, the Planck Survey Scientist, says “It has taken sixteen years of hard work by many scientists in Europe, the USA and Canada, to produce this new image of the early Universe. Planck is working brilliantly and we expect to learn a lot about the Big Bang and the creation of our Universe.”

Reference for Efstathiou quote: UK Space Agency press release 5 July 2010.


Big Cheer for CryoSat-2

30/06/2010

Pick of the pics and Climate Change: News and Comments

Let’s Hear a Big Cheer for CryoSat-2

An early result from ESA’s CryoSat-2 mission detects a “scoop”, or drop, near the edge of Antarctica’s Ross Ice Shelf, probably due to melting at the base of the 400-metre thick slab of floating ice. There are also clear indications of the variable thickness of sea ice in the adjacent ocean. The vertical scale appears to be very different over the shelf and over the sea.

No branch of climate physics has been more befuddled by propaganda than the monitoring of the Earth’s cryosphere. Ordinary melting at glacier snouts that has happened every spring for thousands of years is nowadays captured by TV cameras and presented as evidence of runaway global warming. Dutiful journalists report reductions in Arctic sea ice but ignore increases in Antarctic sea ice. And scientists argue about how thick the sea ice is.

Thank goodness that the European Space Agency’s CryoSat-2 satellite is at last commissioning in orbit. Duncan Wingham of University College London, leader of the project, released the Ross Ice Shelf image yesterday at ESA’s Living Planet Symposium in Bergen.

The mission had a difficult history, with the original CryoSat being lost on launch in 2004, and CryoSat-2 going into an incorrect orbit in April of this year. But now we can expect much more accurate radar measurements of ice altitude over land and ice shelves, and of “freeboard” in the case of sea ice, which is a measure of its thickness. Perhaps we’ll soon begin to get the hard facts about “polar melting”. They’re long overdue.

For another take on “polar melting”, see my history of the Greenland ice sheet at https://calderup.wordpress.com/2010/05/06/warming-of-greenland/


Star positions matter

18/06/2010

Updating The Chilling Stars

Why star positions matter for climate physics

The Making of History’s Greatest Star Map is an excellent account of the European Space Agency’s Hipparcos mission by the project scientist, Michael Perryman. It brings back vivid recollections:

  • of dismay after the launch in 1989, when the satellite failed to go into the right orbit and frantic steps were needed to improvise a survivable orbit and re-configure the observing programme.
  • of satisfaction when operations continued despite unplanned exposure to the Earth’s radiation belts, as well as some nasty solar flares, until the radiation damage became fatal in 1993.
  • of the appetizer in 1994, when early results of the Hipparcos star mapping helped in accurate prediction of the impacts of the fragmented Comet Shoemaker-Levy 9 on the planet Jupiter.
  • of joy on Isola di San Giorgo, Venice, in 1997 when the Hipparcos science team announced their first large-scale results, after a huge computational effort.

Hipparcos in an ESA impression

Astrometry took that great leap forward 30 years after Pierre Lacroute of the Strasbourg Observatory first proposed a space mission to measure the positions of stars, 20 years after Erik Høg of the Copenhagen Observatory refined the concept, and 17 years after ESA earmarked it as something to do. Ground-based astrometry had stalled, because of imprecisions due the turbulence of the atmosphere, and its remaining aficionados had little lobbying power. As a result, Hipparcos remained a distinctly European space project – the first in which there was no competition with the US or Soviet space science programmes.

Applications of the Hipparcos Catalogue of 100,000 plus stars and the Tycho 2 Catalogue with 2.5 million stars (to a lesser but still unprecedented accuracy) have ranged from detecting a bend in the Milky Way Galaxy to checking Einstein’s theory of gravity, General Relativity. But wanting to pursue here the relevance of Hipparcos to climate physics, I’m pleased to see that Michael Perryman points the way.

Michael Perryman. Photo by Richard Perryman

In The Making of History’s Greatest Star Map, pp. 236-243, Perryman notes the role of Hipparcos in refining observations the wobbles of the Earth’s axis, which are involved in the pacing of ice ages (the Milankovitch theory). Then he points to the link between solar activity and climate change, as evidenced by the Little Ice Age, the Medieval Warm Period and other variations. As to the mechanism for the solar connection, Perryman singles out the suggestion that cosmic rays, modulated by solar activity, influence cloud cover.

He continues the story with the Sun’s journey through the Galaxy and the icy intervals on Earth that correspond to exposure to intense cosmic rays when passing through spiral arms. That’s a major topic in The Chilling Stars and, as Perryman says, the Hipparcos data have improved our knowledge of motions in the Galaxy.

It’s reassuring when a professor of astronomy with no scientific or political axe to grind gives serious attention to the cosmic-ray/climate link (the Svensmark hypothesis). Let me reciprocate by reviewing what’s said about the climate-related significance of Hipparcos and its successor Gaia in The Chilling Stars and see if it needs updating or extending.

Read the rest of this entry »


Sprites fight

11/06/2010

Pick of the pics and Climate Change: News and Comments

Sprites fight in the upper atmosphere

Two enormous electrical discharges called sprites are seen brushing together in this conflation of a series of high-speed TV images, looking out over the sea from Catalonia towards Italy. The scale shows the heights above sea level, with the whole phenomenon stretching from 50 to 83 km altitude, and all over in a matter of milliseconds. Source: Joan Montanyà et al., see references.

The following video is in Spanish, but it includes the event shown as a still image above, fully animated. http://plataformasinc.es/index.php/esl/videos/detalle/54380

You can see other video examples of high-altitude  phenomena called sprites, elves and jets in the first image on this ESA page http://www.esa.int/esaCP/SEM4HV4Y3EE_index_0.html

Sprites, elves and jets link thunderstorms and the upper atmosphere, as in this diagram from the National Space Institute in the Technical University of Denmark (DTU).

If “elve” (not “elf”) bothers you in the diagram, be aware that elves is a joky acronym: “emissions of light and VLF perturbations from electromagnetic sources”.

The European Space Agency is preparing an experiment called the Atmosphere-Space Interactions Monitor (ASIM) to observe these events from the International Space Station. The word is that it’s due to fly in 2013.

As for the link to climate physics, here’s a comment made by the ASIM principal investigator a few years ago:

“The question is how are these giant flashes of lightning created and how often do they take place”, says senior scientist Torben Neubert, head of the project at the Danish National Space Centre.

It may well be that the large electrical bursts remove ozone from the atmosphere, and in so doing influence the climate. “We need to understand the natural processes which influence the atmosphere and this can help us decide which changes in the climate are man-made”, Torben Neubert states.

It’s hard to resist pointing out a moral in this tale. Seafarers and mountain-dwellers have noticed these high-altitude lightning flashes for centuries or millennia. They may have provoked some religious experiences. Back in 1925 C.T.R. Wilson, who invented the cloud chamber, predicted the creation of very energetic “runaway” electrons by thunderstorms. In 1956, at the age of 87, Wilson at last saw the high-altitude phenomenon for himself. So did airline pilots and UFO watchers.

Yet our know-it-all meteorologists scorned the existence of sprites until 1990, when 74-year-old John Winckler from the University of Minnesota reported that he had caught a brief image with a low-light TV camera that he was testing. So what else don’t we know, or what are we ignoring, about events and processes at the Earth’s frontier with outer space?

For an impression of how lively this field of research now is, see the titles in http://hydrology.agu.org/contents/sc/ViewCollection.do?collectionCode=THUNDER1&journalCode=JA

References

J. Montanyà et al.,”Intensified high-speed video recordings of sprites and elves over the western Mediterranean Sea during winter thunderstorms.” Journal of Geophysical Research 115, A00E18, 8 PP., 2010

Press releases are available in English http://www.alphagalileo.org/ViewItem.aspx?ItemId=78164&CultureCode=en

and in Spanish http://www.plataformasinc.es/index.php/esl/Noticias/Graban-en-video-a-los-duendes-y-elfos-de-las-tormentas

Neubert quote from http://www.esa.int/esaCP/SEM4HV4Y3EE_index_0.html

C. T. R. Wilson, “The acceleration of Beta-particles in strong electric fields such as those of thunderclouds”, Proc. Camb. Philos. Soc., 22, 534, 1925

J.R. Winckler et al., “Television image of a large upward electrical discharge above a thunderstorm”, Science, 249, 48-51, 1990.


Soil H2O from space

06/06/2010

Pick of the pics & Climate Change: News and Comments

Soil moisture around the Amazon, gauged from space

A plot of microwave “brightness temperatures” measures the water content of the soil around the lower Amazon. This is an early result from Europe's Soil Moisture and Ocean Salinity satellite, SMOS, launched in November 2009 and formally operational since late May 2010. It's a sample of what is now becoming available globally every 3 days, and SMOS should help to fill a huge gap in human knowledge of the water cycle. Credit: ESA/SMOS.

Despite repeated claims that the weather system is known well enough for making multi-decade forecasts of the changing climate, the ignorance can be truly profound. The global water cycle is a key theme where understanding is poor and reliable data are notoriously scanty. The Intergovernmental Panel on Climate Change avoids forthright language that might dismay those who want to treat its findings as gospel, yet in relevant parts of Working Group I’s 2007 report there are hints of desperation. See Section 3.3: “Changes in Surface Climate: Precipitation, Drought and Surface Hydrology”, available here: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-3.html

Soil moisture is crucial

  • as a climate factor in its own right, vital for natural and cultivated plant growth, and for the management of water resources
  • as a strong influence on the global carbon cycle by its contribution to terrestrial photosynthesis
  • as a way station in the hydrological system’s non-stop traffic between rainfall, evaporation, transpiration from plants, and run-off into streams and rivers.

If you want ever to model the water cycle accurately, you really must know the soil moisture content. The European Space Agency claims for SMOS an accuracy of 4%, “comparable to detecting one teaspoon of water mixed into a handful of soil” from an altitude of 760 km. A calculation gives the water content in soil to a depth of 1-2 metres – the root zone.

How’s it done? The presence of water affects the electromagnetic behaviour of soil, and hence the intensity of radio microwaves that it radiates. But the long wavelength, about 20 cm, of the most useful microwaves implies that you need a large radio telescope in space to observe them well.

SMOS, pictured by ESA

The L-band radiometer on SMOS, called MIRAS, uses the radio astronomers’ technique of aperture synthesis. It simulates a much bigger antenna with 69 small antennas strung out along three arms arranged in a Y, and so resolves areas 50 km wide within a hexagon on the Earth’s surface about 1000 km across.

The same instrument on SMOS gauges the saltiness of sea water, using the electromagnetic contrast between pure water and salty water – hence “Ocean Salinity” in the mission’s name. But that’s another story.

Good luck to mission manager Susanne Mecklenburg, mission scientist Matthias Drusch, and all the SMOS team.