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Giotto at Halley: 30 years ago!

OliUsher14 March 2016

pencil-iconWritten by Professor Andrew Coates, UCL Mullard Space Science Laboratory

It was the year of the tragic Challenger disaster – but UCL-MSSL was making good news in space and making history too. The Giotto spacecraft carried 10 instruments, including one led by UCL-MSSL just 596 km (MSSL-ESOC!) from comet Halley on the night of 13th/14th March, with some spectacular results.

Giotto was ESA’s first solo interplanetary space mission, launched in 1985 on the penultimate Ariane 1 rocket. In many ways ESA itself can be thought of as ‘coming of age’ with this first bold step on its own out of Earth orbit. To date, Giotto collected the most complete set of data we have from a comet – the famous comet Halley.

Giotto approaching Comet Halley

Giotto approaching Comet Halley

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Mapping the Apollo landing sites

OliUsher29 September 2014

Lunar Orbiter Photographic DataApollo 11, which touched down in the Sea of Tranquility on 20 July 1969 was the first manned landing on the Moon. But prior to the human spaceflight project, NASA explored the Moon with robotic probes. One key element of this endeavour was the Lunar Orbiter programme, which included five spacecraft that mapped almost the entire lunar surface in 1966 and 1967. This was in part in order to identify landing sites for Apollo, but the missions also had broader scientific goals.

Shortly before the first manned landing, NASA published a catalogue of all their data from the Lunar Orbiter programme, entitled Lunar Orbiter Photographic Data. This features maps of the entire Moon, with the locations, sizes and shapes of all Lunar Orbiter photos marked on them, along with extensive technical information.

Today, missions like this work entirely online, but in those pre-internet days, the data had to exist in hard copy.

A copy of this book exists in UCL’s planetary science archives, the NASA Regional Planetary Imaging Facility. Among its pages is the mapping of the area Apollo 11 landed in, the Sea of Tranquility (Mare Tranquilitas here). This is located towards the right of this sheet, where the imaging (marked in red) is densest.

Lunar Orbiter V - Sea of Tranquility

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High resolution images

 

Venus is losing its atmosphere

OliUsher9 July 2014

Mars, Earth and Venus are very similar in many respects.

They are all rocky planets of roughly similar size; all three have atmospheres, weather and seasons, as well as extensive ranges of mountains and canyons on their surfaces.

But in other respects they are quite different.

Earth’s atmosphere is generally placid. But on Mars, it is so thin that liquid water cannot exist at any temperature, and on Venus, the atmospheric pressure is equivalent to diving almost 1000 metres into the ocean. On Mars, temperatures rarely venture above 0°C and can drop below -100°C; Venus meanwhile has surface temperatures of over 450°C, hot enough to melt lead.

The thin atmosphere of Mars is thought to be due to the planet’s lack of a magnetic field, which has allowed the Solar wind to blow away much of the gas the planet once had.

Venus, despite still having a thick atmosphere of CO2, surprisingly has a similar problem. Venus also lacks a magnetic field, and it is losing gas at a similar rate to the red planet.

The interaction of the Solar wind with the Venusian atmosphere has been studied by the Venus Express probe, which has been orbiting the planet since 2006.

Computer rendering of ESA's Venus Express probe. Credit: public domain (Celestia)

Computer rendering of ESA’s Venus Express probe. Credit: public domain (Celestia)

Like many ESA space missions, UCL was intimately involved in the design and construction of the scientific apparatus on board. In the case of Venus Express, this involved a leading role in the development of the electron spectrometer on board, as well as building the shielding and carrying out the calibration for the detector.

This detector has been able to measure the varying rate at which the atmosphere is being lost.

Venus Express is currently entering the final stages of its mission. The spacecraft is being brought progressively closer to the planet’s surface, skimming through the upper atmosphere. The friction of the tenuous gas is enough to heat the probe up, and to further slow it down, bringing it closer still. This process of aerobraking will eventually destroy Venus Express, but in the process, its instruments will be able to gather valuable scientific data about the planet’s upper atmosphere, including – thanks to the electron spectrometer – its electrical properties.

Postscript

No NASA or ESA probe has ever reached the surface of Venus. But a series of bold Soviet missions in the 1960s, 70s and 80s made several landings on the surface, as well as a balloon that floated through the planet’s atmosphere. The Venera probes revealed a rock-strewn landscape in the few minutes they were able to survive before being destroyed by the high temperatures and pressures there. More information on the Venera 13 and Venera 14 pictures held by UCL’s planetary science archives can be found on the archives’ space history webpages.

Photograph of the surface of Venus from Venera 13. Photo: public domain (National Space Science Data Center)

Photograph of the surface of Venus from Venera 13. Photo: public domain (UCL/NASA Regional Planetary Image Facility)

Mars Express and the magnetism of the red planet

OliUsher8 July 2014

Planet Earth is a vast magnet with a strong magnetic field surrounding it. As well as making compasses point north and guiding solar particles to the poles, creating the aurorae, the magnetic field protects our atmosphere. Shielded from the solar wind and from solar and galactic cosmic rays, Earth’s atmosphere is thick and life-sustaining and is not at any risk of being blown into space.

Mars – an Earth-like planet in many other respects – has lacked such a global magnetic field for about 3.8 billion years. Its atmosphere is thin – less than 1% of the atmospheric pressure we have on Earth – leaving a cold, hostile and barren surface.

The magnetic fields of Earth (left) and Mars (right). Earth has a strong, planet-wide magnetic field that shields our atmosphere from the Solar wind. Mars has only small localised areas of magnetism. Credit: NASA/GSFC (public domain)

The magnetic fields of Earth (left) and Mars (right). Earth has a strong, planet-wide magnetic field that shields our atmosphere from the Solar wind. Mars has only small localised areas of magnetism called crustal fields, meaning its atmosphere interacts directly with the Solar wind. Credit: NASA/GSFC (public domain)

The lack of magnetic field makes Mars different from Earth in other respects too. In fact, in some ways Mars behaves much like a comet: since the Solar wind interacts directly with the atmosphere a comet-like tail of gas is constantly being blown off the planet (albeit not to the extent of a comet as it passes near the Sun).

UCL researchers have studied the behaviour of Mars and its interaction with the Solar wind for many years, including through participation in the European Space Agency’s Mars Express mission. Orbiting Mars since 2003, the mission has been a huge success (unlike the Beagle 2 lander it carried), and like many missions it carries UCL hardware contributions. This comes in the form of a sensor in the ASPERA-3 instrument, for which UCL carried out calibration and blackening (to prevent internal reflections degrading observations) prior to launch.

Computer rendering of the Mars Express probe. Credit: NASA/JPL (public domain)

Computer rendering of the Mars Express probe. Credit: NASA/JPL (public domain)

The ASPERA-3 instrument has helped UCL scientists study Martian magnetic anomalies called crustal fields. These are small, localised magnetic fields on the surface of Mars which interact with the Solar wind and material escaping the Martian atmosphere. It has also observed how the faint ‘tail’ of material streaming from Mars has photoelectrons caused by the Sun.

UCL is also involved in the exploration of the Martian surface – it leads the team building the main camera for the ExoMars Rover, Europe’s first Mars rover, which touches down in 2019.

The Alfvén conference, being held at UCL this week, is bringing together experts from around the world in the field of electrical, magnetic and plasma interactions in the Solar System. Today’s focus is Mars. Among the presentations will be new research on the data sent back by Mars Express, as well as the latest news from NASA’s MAVEN mission and India’s Mars Orbiter Mission, both on route to the red planet with expected arrival in September 2014.

This evening there will be a public lecture at UCL about the Rosetta mission, which is currently approaching Comet C-G. Matt Taylor, the scientific leader of Rosetta, will outline the probe’s amazing ten year journey, outline Rosetta’s scientific goals and explain why comets are such an important window into the distant past of our Solar System. The lecture is free and open to all, but please reserve your seat as spaces are limited.