Many students send emails requesting summer internships at UCL Physics & Astronomy, but one particularly caught Dr Anasuya Aruliah’s eye. Vishal Ray was a 2nd year Aerospace Engineering undergraduate at the prestigious Indian Institute of Technology Bombay, India (IIT). He belonged to a student team building their own miniature satellite. Vishal was just the student that Dr Aruliah needed for her new direction of research: satellite drag. After a successful application to the International Students Dean’s Summer Student Scholarships, he was awarded a 2 month internship in summer 2015.
Dr Aruliah’s group, the Atmospheric Physics Laboratory (APL), is a subgroup of the Astrophysics Group. It has a long history of researching the upper atmosphere using a global circulation atmospheric model. They also operate a network of Fabry-Perot Interferometers (FPIs) in Arctic Scandinavia to observe the aurora. The Earth’s atmosphere is like an onion skin, with the troposphere (the domain of weather forecasters), stratosphere and mesosphere as layers on top of each other. The thermosphere is the final layer of the Earth’s atmosphere, and is the altitude region between 90-400km. Low Earth Orbit (LEO) satellites occupy the top of the thermosphere, and rely on upper atmospheric models to predict their orbits.

Recently the APL group found a discrepancy between measurements of thermospheric winds calculated from Doppler shifts of airglow photons, and winds determined from atmospheric drag on the Challenging Minisatellite Payload (CHAMP) satellite. This is an important puzzle to solve because satellite drag measurements are put into atmospheric models to bring them as close to reality as possible. If the ground and satellite measurements do not agree, then which is correct?

The IIT miniature satellite, commonly called a cubesat, is composed of a single cube, only 30 cm in length, width and breadth, and weighing only 10 kg, as much as a few bags of sugar. Their cubesat is called Pratham. This fits perfectly with UCL’s involvement in the European Union FP7-funded QB50 project, in which fifty cubesats carrying miniaturised sensors will be launched nearly simultaneously. This is an international collaboration involving many universities, academic institutes and the space industry. It is an unprecedented science operation, with potential for future Space Weather monitoring campaigns. The QB50 cubesats will be carried by rocket into the upper thermosphere, and fall to Earth in decaying orbits while sampling regions of the thermosphere and ionosphere that were previously poorly understood owing to the lack of detailed measurements.

“The simplicity and low cost of cubesats has spurred much excitement and creativity amongst young (and old) engineers and scientists over the last few years. There are new frontiers being opened by this miniaturised space technology,” said Dr Aruliah.

The UCL Mullard Space Science Laboratory (MSSL) designed and built one of the three key sensors: the Ion Neutral Mass Spectrometer, which will be carried on several of the cubesats, as well as their own cubesat called UCLSat. The QB50 cubesats are scheduled for launch in three batches over the winter period of 2016-2017. Two batches from a Ukrainian-Russian Dnepr rocket, and a third from the International Space Station. During Vishal’s internship at UCL he met with the MSSL cubesat and sensor team, led by Mr Dhiren Kataria and Dr Rob Wicks; and with Dr Stuart Grey in the UCL Department of Civil, Environmental & Geomatic Engineering.

Dhiren Kataria holding the UCLSat designed and built at MSSL

Vishal used his experience to write several sophisticated computer programs to calculate drag coefficients from simulations of a cubesat orbiting in our 3-dimensional atmospheric model called CMAT2. This work was subsequently built upon by Dr Aruliah’s 4th year project student, Jennifer Hall. Jennifer wrote her own programs to derive and compare satellite drag coefficients from CMAT2 simulations and EISCAT radar measurements. Jennifer’s project won the UCL Physics & Astronomy Tessela prize for best use of computer technology in a 4th year project.

Pratham team at the Indian Institute of Technology Bombay. Vishal Ray is 2nd from the right in the top row.

One year on, after a busy 3rd year of studies, Vishal has written up his summer project as a journal paper, and “Pratham” was scheduled for launch at 0530 UTC on the 26 September 2016. The IIT Bombay student team installed their cubesat on the launch vehicle PSLV C-35 on the remote island of Sriharikota in South India. Vishal said that he “…had goosebumps when we actually placed the satellite on the launch vehicle module and completed the testing for one last time!”. “Pratham” was successfully launched and will measure the total electron count from 800 km altitude in a Sun Sychronous Orbit. MSSL were the first to receive Pratham’s beacon signal, which the students were incredibly excited to hear. You can hear the cubesat from 4:20 onwards as it passes within range of the detector at MSSL. The signal is decipered as “Pratham IIT Bombay Student Satellite”. The accompanying image is of Theo Brochant De Viliers (MSSL) beside the MSSL receiver.

https://soundcloud.com/uclsound/signals-from-the-pratham-cubesat-satelllite

The prospect of finally being launched is very exciting, with both projects having been nearly 10 years in the making. Once launched, the missions will change from the technical challenges of the innovation of miniature sensor devices to the scientific challenges of collecting, analysing and interpreting the measurements. The rewards will be great: from the new technologies surrounding cubesats; to the training of future space scientists and engineers, and to the Space Weather community.

Written 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 13^th/14^th 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

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What Cassini did for the Saturn system in the 2000s, the Jupiter Icy Moons Explorer (or JUICE for short)  will do for Jupiter in the 2030s.

Artist’s impression of JUICE in the Jupiter system. Credit: ESA (All Rights Reserved)

The European Space Agency mission is currently being developed, with a 2022 launch planned. It will study Europa, Ganymede and Callisto, three of the largest moons in the Solar System. (Ganymede, which JUICE will orbit in 2032, is so big it is larger even than the planet Mercury).

Europa will be a particularly interesting target – the moon is covered by a thick crust of water ice, which may conceal an ocean of liquid water. If so, this could make it one of the most promising location in the Solar System for extraterrestrial life. It is thought that conditions below the ice could be similar to those in Antarctica’s Lake Vostok – a vast body of water that has remained totally covered by 4km of ice for millions of years, but which still harbours life.

UCL will provide detectors for JUICE’s scientific payload (in the form of the IRF-led Particle Environment Package) and will play scientific roles in the Imperial-designed J-MAG instrument, as well as the JANUS imager. It will also contribute more generally to the design of the craft.

As with Cassini, UCL’s contribution will focus largely on electromagnetic phenomena, including the interaction of Jupiter’s satellites with the Jupiter magnetosphere, and the effect of Jupiter on the moons’ atmospheres. The instrumentation will also play a key role in studying the oceans on Europa, Ganymede and Callisto.

UCL is hosting the Alfvén conference this week, in which experts in planetary magnetic fields and plasmas are coming together to discuss the latest news from missions including plans for JUICE.

Last year, after almost a decade of studying Saturn and its moons, the plasma spectrometer onboard the Cassini probe broke down. This was far beyond its planned lifespan of four years – and what’s more, it may yet have second life, with plans to revive it near the end of the mission in 2017.

In addition to its long service at Saturn, the instrument had also survived the long journey through space that had begun in 1997 – a journey in which it was subjected to the harsh environment of interplanetary space, passed Venus twice and made measurements during Earth and Jupiter swingbys.

Artist’s impression of Cassini at Saturn. Credit: NASA (public domain)

Scientists at UCL Mullard Space Science Laboratory took a lead role in the hardware development and the science team for the electron spectrometer, and while it is no longer operating, there is still plenty of work to do on the data it gathered. In particular, the detector’s studies of Saturn’s moon Titan are expected to yield further secrets.

Cassini – a NASA-led Saturn orbiter – released an ESA-built lander called Huygens to land on Titan when it arrived in the Saturn system in 2005. Huygens took the first ever picture on the surface of a body in the outer Solar System. (It is also the only landing to-date on another planet’s Moon.)

Huygens photo of Titan’s surface. Credit: NASA/JPL/ESA/University of Arizona (public domain)

But what the Cassini probe is able to do from space, which Huygens could not on the ground, is analyse the complex interaction of Titan’s thick atmosphere with the magnetic field of Saturn. Titan is surprisingly Earth-like, despite being quite small. It has a thick atmosphere and an icy, rocky surface, as well as mountains, seas, lakes and rivers (though these are made of liquid hydrocarbons such as methane, rather than water).

Hydrocarbon lakes on Titan, observed by the radar onboard Cassini. Radars do not produce colour images – in this picture, the smooth areas (lakes and rivers) have been coloured blue to improve contrast. Credit: NASA/JPL-Caltech/USGS (public domain)

But while Earth’s atmosphere is cocooned well inside our planet’s magnetic field, protecting it from the Solar wind and from interactions with other Solar System bodies, Titan’s is not. Titan spends most of its orbit within Saturn’s hot magnetosphere, meaning its atmosphere interacts with the giant planet it orbits, including the plasma and magnetic field that surrounds it. This makes Titan’s atmosphere very ‘leaky‘ compared to Earth’s.

A recent fly-by of Titan by Cassini while the moon was orbiting outside Saturn’s magnetosphere reveal another intriguing phenomenon: the Solar wind blowing part of Titan’s atmosphere away, leaving a comet-like plume of gas coming from it.

UCL is hosting the Alfvén conference this week, in which experts in planetary magnetic fields and plasmas are coming together to discuss the latest results from missions including Cassini.

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)

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 (UCL/NASA Regional Planetary Image Facility)

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 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)

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.

The European Space Agency’s Rosetta mission, coming to its climax only now, a decade after launch, will have a number of scientific firsts: the first probe to follow a comet around the Sun while it orbits, the first to orbit a cometary nucleus, and the first to deploy a lander on the comet’s surface.

UCL has made a major contribution to the scientific programme the spacecraft, thanks to its long-standing expertise in plasma physics. Much of this expertise was gained in a previous space mission.

Artist’s concept of the Giotto spacecraft approaching Comet Halley. Credit: Andrzej Mirecki (CC-BY-SA 3.0)

In 1986, the Giotto probe flew by Comet Halley, giving the first ever close-up view of a comet’s nucleus. UCL built the probe’s Fast Ion Sensor and led the Johnstone Plasma Analyser team. Thanks to this detector, scientists were able to study the interaction between the comet and the solar wind as the comet ploughed through it, including the enormous bow-shock in front of the comet that extended for around a million kilometres, and the processes by which cometary ions are ‘picked up’ by the solar wind.

Rosetta should give us a lot more than this. Two decades of technological progress mean sharper photos and more sensitive instruments. But the major improvement is in how long the probe will be able to study the comet for, as well as its close-up study of the comet’s ionosphere. Giotto made only a relatively short flyby of Halley, in large part because the comet’s orbit is highly inclined and moves in the opposite direction to Earth’s, and it only passes through the plane of the Solar System on two brief occasions every 76 years. Comet Churyumov-Gerasimenko, Rosetta’s target, is in an orbit that is easier to rendezvous with, which means – with some admittedly difficult and time-consuming orbital mechanics – Rosetta can be brought into orbit around it.

This, in turn, means the changes in the comet, including the growth of its coma, and plasma (gas) and dust tails, can be charted in detail as it proceeds around the Sun.

Computer rendering of the Rosetta spacecraft. Credit: public domain (Celestia)

UCL scientists at the Mullard Space Science Laboratory are particularly closely involved in the Rosetta Plasma Collaboration, a scientific group which will study the electrical properties of the comet as it interacts with the Solar wind. This is a direct continuation of the work done with Giotto nearly three decades ago.

The wait won’t be long now – Rosetta is less than 30,000km from its goal (less than the distance between Earth and geostationary communications satellites), and will begin manoeuvring into orbit in early August. Early data will come sooner, with the first detection of the comet’s plasma expected perhaps as early as this week.

Rosetta is one of a number of missions being discussed at the Alfvén Conference this week at UCL. Named after Hannes Alfvén, a Swedish plasma physicist and Nobel laureate, the conference is bringing together experts from around the world in the field of Solar System plasma interactions, such as those Rosetta will study.

As part of the conference, Matt Taylor, the scientific leader of the Rosetta project will be giving a public lecture tomorrow (Tuesday 8 July) at 6pm. He 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.

In space, space is at a premium.

Launching a satellite is hugely expensive. Every kilogram it weighs and every cubic centimetre it takes up costs money. Spacecraft engineers have therefore had to become experts at miniaturisation – and nowhere is this more obvious than with the CubeSat concept.

CubeSats are a class of tiny spacecraft. They are based on cubes just 10cm along each side, and up to three can be joined together into a single satellite. Thanks to their diminutive size, they can easily piggyback on other launches that have spare capacity, or alternatively many CubeSats can be launched in one go.

The most ambitious CubeSat project to date is a European project called QB50, which plans to send 50 CubeSats into orbit in one launch in early 2016. This will be the largest number of satellites ever put into orbit on board a single rocket.

Each of the satellites will be built by a separate institution from around the world (including one – UCLSat – by UCL’s Mullard Space Science Laboratory). Up to 40 of them will sport sensors that can probe the properties of the upper atmosphere. The consortium providing the sensors is led by UCL MSSL, which will build 14 spectrometers that will analyse the relative proportions of different types of particles in the thermosphere.

The Ion & Neutral Mass Spectrometer, designed and built at UCL, prior to being attached to the CubeSat. The device is less than 10cm across.

As the orbits of the 50 satellites gradually decay, they will spread apart, giving a unique opportunity to measure the upper atmosphere in multiple locations at the same time, using the same type of instrumentation.

QB50 is an ambitious programme, and so a precursor mission using just two satellites is now underway. Launched on 19 June from the Russian space centre at Yasny, the precursor satellites have a UCL-built Ion and Neutral Mass Spectrometer (INMS, which measures atomic and molecular oxygen, along with molecular nitrogen) and a Flux (Phi) Probe Experiment (FIPEX, which detects atomic and molecular oxygen) procured from the Technical University of Dresden.

The two complete satellites for the QB50 precursor flight. THe satellite on the right has an Ion Neutral Mass Spectrometer, built by UCL, attached to its top surface. The satellite on the left has a Flux (Phi) Probe Experiment, designed by the Technical University of Dresden

As well as being very small, the instrumentation for the QB50 test mission had to be developed very fast, over a period of just a few months. Mission approval came in October 2013, and the completed satellites had to be delivered to the launch site in May 2014.

A further test of UCL’s miniaturisation technology will come with TechDemoSat, a UK satellite that launches on 8 July, and NASA’s Sunjammer mission in January next year.

Dhiren Kataria (right), the MSSL detector physicist behind the QB50 INMS instrument. Behind him, the CHaPS payload for the forthcoming TechDemoSat mission (based on the same technologies as QB50 INMS) being prepared for testing in a calibration chamber

Artist’s impression of Mariner 10. Credit: NASA/RPIF/UCL Earth Sciences (public domain)

Of all the planets of the inner Solar System, Mercury is the least-visited. No mission has ever landed on its surface, only two missions have studied it from space, and only one of those has reached orbit.

Travelling to Mercury is difficult as the proximity to the Sun makes for unstable orbits and fast orbital speeds.

The first spacecraft to visit Mercury was Mariner 10, pictured here in an artist’s impression from UCL’s planetary science archives. UCL is the only UK institution to host a NASA Regional Planetary Image Facility.

Mariner 10 made three fly-bys of Mercury in 1974 and 1975, mapping a little under half of the planet’s surface.

The complex path to Mercury, involving multiple fly-bys, was designed by scientist Bepi Colombo, whose name is honoured by a forthcoming mission planned by the European Space Agency and the Japan Aerospace Exploration Agency. The BepiColombo mission, expected to launch in 2016, will feature two orbiters, and will fly past the planet several times before reaching orbit in 2024.

UCL’s Prof Alan Smith is chair of the UK Space Agency’s BepiColombo management board.

Image credit: NASA/RPIF/UCL Earth Sciences

Links

• Snapshots from Space History (UCL RPIF public outreach website)
• UCL Regional Planetary Image Facility
• UCL Earth Sciences
• UCL Mullard Space Science Laboratory

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