Summer School Alpbach 2013: "Space Weather: Science, Missions and Systems"

It has been a hard 10 days, these last two weeks, when I was playing tutor at the  Summer School Alpbach 2013.

On Monday 16 July a group of 60 European students arrived in Alpbach (Tyrol, Austria) to learn about and work on the topic of Space Weather. Split into four groups (Red, Green, Blue and Orange) they were subjected to a rigorous program of lectures in the morning and workshops in the afternoon and evening (and ultimately in the night). The lectures varied from Solar Physics and Space Physics to Satellite Mission Design and Risk Management. After the first full day of lectures and a nice BBQ, the different groups sat together and got acquainted with each other. But then after the second day of lectures the real work started, each group sat in its own classroom and had to come up with ideas for a Space Weather Mission for ESA.

Needless to say that it was arranged by the organizer of the summer school that I was given Team Orange as science tutor together with Jaan Praks as an engineering tutor.On Tuesday afternoon Peter Falkner presented the different groups and "my" team (names listed below)  knew it was doomed to spend the rest of the time with the weird guy with the orange hat.

After the common dinner at Böglerhof, we went down to the school again to start thinking about a project. Just let your imagination flow and see what comes out. Various ideas were presented, from having electric sails in a constellation along the Parker spiral; a set of satellites flying from Earth to Mars, staying there for a while and then come back to Earth to measure the total dose of radiation that astronauts; a constellation of 4 spacecraft around the Sun near Venus's orbit to scan for Coronal Mass Ejections (CMEs) - but there we were "outbid" in the end by Team Blue who proposed six! - and a closer to Earth project to study the influence of the Sun on the Earth's thermosphere and ionosphere.

Adonis stands for
"Atmospheric Drag, Occultation 'N' Ionospheric Scintillation."

After a lot of discussions, and a bit of restriction from the Summer School Jury (no solar or electric sails) it was decided that we would work on the last project and thus on Wednesday evening, just before dinner, when Jaan and I were in the Tutor Meeting (or the beer party as the team used to call it) the project that would eventually become the Adonis Mission was chosen.

Deep Thought:
not only a computer,
but also a state of mind
in Alpbach

Here Team Orange tries to come up with a mission to investigate the upper layers of the Earth's atmosphere. If the energy input of the Sun into the Earth's systen changes (e.g. during a strong solar flare or the impact of a CME on the magnetosphere) then the characteristics of the thermosphere and ionosphere are changed. An example is the drag of the atmosphere on satellites, which increases strongly with solar activity. During the Halloween magnetic storm the International Space Station dropped suddenly 15 km because of the increased drag on it by the atmosphere. Another example is the loss of signal with e.g. GPS satellites or loss of communication because of changes in the ionosphere.

Three bottles of
"Alpbach Beer" cooling
for the final celebration.

To investigate these topics, two satellites in Low Earth Orbits (LEOs) were proposed, in elliptical polar orbits, which would measure the drag on the satellite with an accelerometer and indirectly measure the electron content of the ionsphere through measuring the signals from GPS and other spacecraft (occultation) and signals from ground stations (scintillation). And not to be overly ambitious, Team Orange decided that this should be measured over a full solar cycle. The team worked hard and late (0130 CEST was considered early in more ways than one). The reason for working so hard (apart from it being so much fun): Wednesday evening at midnight the project consising of a 10 page document and a one hour presentation should be delivered to the jury, including the laptop from which the presentation would be projected. This great team did it with time to spare! 2350 CEST everything was delivered, just sligtly behind Team Red, who came in first (congrats to them). Time to celebrate! Open up the sligtly cool bottles of Alpbach beer.

Michaela Gitsch, blindfolded, draws
the next presenting team to from
the box, helped by
Michel Jakob (l) and Peter Falkner (r).

On Thursday was the big event, when all teams would have to present their projects in front of all other teams and a distinguished jury. Michaela Gitsch drew - blindfolded - the team that was to come up and speak. Team Orange was drawn out of the box just after lunch, to present as third team. They did a great job at presenting, keeping within time and answering the questions from the jury very well. Some jury members were skeptical, but that did not waver Team Orange, and after talking to a skeptical jury member, they even got the advise to pursue a publication on the topic, so it can't have been that bad, eventually.

Half of Team Orange
at the Grand Dinner

That evening after the Grand Dinner, the Oscars for the projects would be presented by the president of the jury Roger Bonnet (do you know about reconnection?) with the following result:

• Best Science Definition: Team Green
• Best Technical Case: Team Red
• Head Tutor - Steepest Learning Curve: Team Blue
• Most Competitive: Team Orange
• Best Presentation: Team Green

Roger Bonnet just handed
the Oscars to Team Orange

So  I must say I am very pleased with the result that Team Orange achieved, because being "most competitive" means you are most likely to get funded and to fly. And thus, following the Oscar tradition (even though I did not get one) I would like to thank the following people:

• Martina Edl
• Francesco Gini
• Linn-Kristine Glesnes Odegaard
• Nina Magnet
• Jedrzej Gorski
• Sebastian Hettrich
• Yann Kempf
• Nikolaos Perakis
• Owen Roberts
• David Sarria
• Maximilian Schemmer
• Stefan Schindler
• David Steenari
• Jaroslave Urbar
• Melinda Verebelyine Dosa

AKA TEAM ORANGE, who I encourage to try and finish a full paper on this interesting topic (I will give full support there). Thanks for a wonderful two weeks, and naturally also thanks to my co-tutor Jaan Praks

Last impression of the classroom
with Jaan sitting in the middle

Me, Peter Falkner and Manuela Temmer

So, now it is time to rest and gather strength for the "Post Alpbach" from 9 to 13 December in Graz. The jury chose the challenging project of Team Blue (6 spacecraft at Venus's orbit monitoring the Sun for CME warnings) to be further developed by a select group of 15 participants of the Summer School. I am sure I will see some of Team Orange back again.

Aurora and the Earth’s Magnetotail Part 3: THEMIS and beyond

Power transformer in New Jersey, US, burnt
out due to induced current caused by a
geomagnetic storm in March 1980.
(courtesey PSE&G)

In March 1998 there was a strong magnetic storm which created currents in the Earth's magnetosphere and induced currents also in the electricity network. Strongly changing magnetic fields will induce electric fields in conductors, and thereby electric currents. If the electrical system is not optimized or switched off (which mostly happens with satellites in space) then during strong events the induced current can become so great that it burns transformers, like the example in New Jersey. In order to avoid this kind of damage one needs to study Space Weather (apart from updating the power grid to modern standards).

THEMIS view of the Magnetotail

The THEMIS spacecraft in the clean room
mounted on their launch platform.

On 17 February 2007 the 5-spacecraft mission THEMIS (Time History of Events and Macroscale Interactions during Substorms) were launched, which had the goal to study the dynamic processes in the Earth's magnetotail at 5 different locations along the tail.They were put into elliptical orbits with apogees (furthest distance from Earth) at 10 (2x), 12, 20 and 30 Earth radii, and with every full orbit of the outermost satellite, the five would line up along the tail.This way, the development of the explosive events leading to aurorae, substorms, can be studied in space and time through simultaneous observations by identical spacecraft.

All the processes in the Earth's magnetotail that lead to the reconfiguration of the magnetic field, through stretching, reconnection, fast flows and generation of the aurora are called a magnetospheric substorm. The word substorm is a bit antiquated, because in the beginning people thought that a geomagnetic storm (another energetic phenomenon of the Earth's magnetosphere, which lasts much longer) was build up from a set of smaller substorms. Although this idea was proven wrong, the name substorm stuck.

The "outside-in" model for substorms

There has been, and still is, a longstanding discussion about the processes during such a substorm, where basically two schools stand face-to-face. One side says: "A substorm starts by reconnection far down the tail and then processes closer to the Earth happen and the aurora is created," which is the so-called "outside-in" group. The other side, unsurprisingly, says: "At a substorm first something happens close to the Earth, which sends a signal out, which sets on reconnection further down the tail and then the aurora is created," which is the "inside-out" group. THEMIS was supposed to solve this problem.

The "inside-out" model for substorms

In 2008 the first and conclusive paper was published in Science by the PI team: Tail Reconnection Triggering Substorm Onset. This should show that the "outside-in" model was the correct interpretation of how substorms develop. However, one can imagine that this was not the end of the story, the other group wanted to have a say too. After many (heated) discussions at scientific conferences a paper was published in the Journal of Geophysical Research in 2011: Revisiting Time History of Events and Macroscale Interactions during Substorms (THEMIS) substorm events implying magnetic reconnection as the substorm trigger, where some critical notes were made on the interpretation of the original paper, showing that the case may not be so clear as originally was thought and that the "inside-out" model could be the correct interpretation. Well, fortunately, one can find still other events that do not seem to care at all about these two schools and do not adhere to either. This will keep space physicists busy for the next coming years, if not decades. And there is a important thing to be learned here, also in space physics things are not black or white, in complicated processes like substorms there are at least 50 shades of grey. Don't get hung up on just one interpretation.

Unfortunately THEMIS is no longer. The spacecraft are still in space and working, but the mission has changed. The two outermost spacecraft have had their orbits majorly changed and were send to the Moon in 2011, where they now operate under the name ARTEMIS. The three innermost spacecraft remained in their near-Earth orbits.

The next big multi-spacecraft mission for the Earth's magnetotail is going to be NASA's Magnetospheric Multi Scale (MMS) mission, which is going to be another 4 spacecraft mission, similar to Cluster in a tetrahedron configuration, but now the spacecraft will be much closer together, 30 - 400 km. MMS will look at the dynamic processes in the tail at the "electron scale." Basically, this mission will "zoom in" on e.g. the reconnection process that was measured by the Cluster mission and get a more detailed view on smaller scales of what is going on. The planned launch is in October 2014.

Aurora and the Earth’s Magnetotail Part 2: From Birkeland to Cluster

On 21 December 1833 "The Penny Magazine" had a drawing of the aurora on its front page. The corresponding article reads "The Aurora Borealis is a beautifully luminous meteor, appearing in the form of streams of light, rays, arches and crowns. A description of this splendid phenomenon, which enlivens the long darkness of the Arctic regions, has been given by Mr. A. De Chapell Brooke, in his 'Winter in Lapland' to which work we are indebted for the subject of our cut."

As per the end of the last post, we will start this story in 1963.

A Rocket in the Aurora

Magnetic field measuremens of
the US Navy rocket 1963-38C
showing the strong transverse
field fluctuations

After the start of the space age, basically starting with the launch of Sputnik on 4 October 1957, the investigation of the upper layers of our atmosphere also started to be done with so-called sounding rockets. The US Navy rocket 1963-38C was launched up into the ionosphere (100 - 600 km above Earth's surface) and it was equipped with magnetometers. When the rocket crossed the auroral regions strong transverse (i.e. perpendicular to the background field) magnetic field fluctuations were observed. This is a clear indication of the presence of magnetic field aligned currents (although it was first thought that they were hydromagnetic waves), the ones that Birkeland proposed to exist in the auroral regions. However, when the finding was published, there was no mention of Birkeland or of the currents. But as space missions continued, more and more evidence for these field aligned currents was gathered. Nowadays these are called Birkeland currents.

What is the source?

A simple model of the Earth's
magnetosphere, with the solar wind
(orange) interacting with the Earth's
magnetic field

To understand the generation of these Birkeland currents we have to understand how the solar wind interacts with the Earth's magnetosphere. The solar wind consists of a hot ionized gas (or plasma) which flows out of the Sun and embedded in the flow is the solar magnetic field. Due to the radial outflow of the plasma and the rotation of the Sun, the magnetic field gets rolled up around the Sun on its way outward, which creates the so-called Parker spiral. The solar wind interacts with the Earth's magnetic field in various ways, depending on the direction of the solar wind magnetic field. If the field is pointing up (i.e. northward) then the solar wind just compresses the Earth's magnetic field, and (keeping it simple) things remain quiet. However, if the field is pointing southward, it has the opposite direction as the Earth's magnetic field at the front, and then things happen, but let's first take a quick look behind the Earth.

At the front of the Earth the magnetic field is compressed by the solar wind. At the back of the Earth, however, the magnetic field gets pulled along with the solar wind and is stretched into a long tail. This stretched magnetic field, like a stretched rubber band, can store a lot of energy that can be released after a certain trigger is pulled.

The simplest version of magnetic
reconnection, field lines are pushed
together in the middle, and at the
central part (the X-point) new
connections are made and the tension
of the fieldmoves the field lines away from
the X-point

When the solar wind turns southward, the solar wind magnetic field connects itself to the Earth's magnetic field, opening up the magnetosphere at the front. This process is called magnetic reconnection. The continuous flow of the solar wind pulls along the magnetic field, and thus at the front the field is stripped off, and transported to the back of the Earth, where it is added to the magnetotail. One can, however, not keep on adding magnetic field to the magnetotail without end, and something drastic happens. In the centre of the tail, where the magnetic field is oppositely directed in the northern and southern part, the field gets squeezed together enough to start the same process as at the front, reconnection. The stretched magnetic field in the tail explosively reconnects and shoots the plasma towards the Earth and away from it, depending on which side of the reconnection point you are watching.

The "complete" solar wind - magnetosphere
interaction

This reconfiguration of the magnetotail, from very stretched and full of stored energy, to a less stretched lower energy shape, brings along the generation of currents, as with every temporal change of a magnetic field (e.g. a bicycle dynamo where a rotating magnet generates currents in a wire coil, which then let the light bulb shine). These (Birkeland) currents and highly accelerated particles flowing along the magnetic field towards the Earth create the aurora through their interaction with the Earth's atmosphere.

Exhibition models of the four
Cluster spacecraft

In 2000 the four-spacecraft Cluster II mission was launched. Four spacecraft that would be flying in a tetrahedron shape in regions of interest of the Earth's magnetosphere. All four spacecraft carry the same instruments and thus there are simultaneous measurements  of various quantities like magnetic field strength, plasma properties, etc. at four different points. Due to the specific configuration of the spacecraft this helps understanding the processed that are taking place in the magnetosphere, because we can now find out whether signals that are observed are caused by spatial of temporal structures.

Magnetic field measurements by
Cluster at three different locations
around a reconnection region and
an artist's impression of how the
spacecraft moved though this region.

This mission was used to make measurements in the magnetotail and in October 2001 an event was measured which showed clear signatures of this reconnection process [Runov et al., Current sheet structure near magnetic X-line observed by Cluster, 2003] . The spacecraft flew through the region where the field lines get together and reconnect and flow out again, like the moving image above. All the parameters that were measured were in agreement with the picture of magnetic reconnection. Cluster started at point A, where the plasma moved towards the tail region (away from the Earth) and then crossed a region where the field gets together (B) and then entered a region where the plasma moved towards the Earth (D). The direction of the magnetic field also agreed with the picture above and the extra magnetic fields that should be present because of the extra currents that flow in the reconnection region were also measured.

So now we have found the driver for the energetic processes which generate the aurora. In the next part we will take a look closer to Earth again, the region just above the aurora. We will try to follow the processes along the magnetotail with the THEMIS mission. And we will take a closer look at how the Earth's magnetosphere reacts at the dayside to changes in the solar wind magnetic field direction.

Aurora and the Earth’s Magnetotail Part 1: From History to Birkeland

On 1 August 2010 there was a huge explosion on the Sun, sending out a large cloud of plasma and magnetic fields (a so called Coronal Mass Ejection or CME) which hit the Earth on 3 August, creating majestic aurorae (great pictures of aurorae by Emil Kepko) even at low latitudes. What happened here? Before we answer that, we will first take a little trip through history and look how the study of aurorae and modern space physics developed. 

History

Anders Celcius

In  1716 there was large scale auroral activity over Europe, which fascinated the natural scientists of that time, like Anders Celcius. Naturally, due to their geographical location the Scandinavians have had a leading role in the study of the northern lights. Together with Olof Hiorter Celcius decided to look at how a compass needle behaves, and therefore they wrote down the compass needle reading every hour for a whole year. What they found was that every time there was auroral activity the needle of the compass would change direction and wiggle. The stronger the aurora, the more the compass needle moved, and thus is was decided that aurora is “magnetic in nature,”  however a model for how this works exactly could not be given by these two researchers. Alexander von Humboldt would later call this phenomenon a “magnetic storm” (a term still used in modern space physics). These people were on the right track.

A solar pillar

However, there were also other proposed mechanisms that were, as we now know, incorrect. The director of the observatory of Vienna’s university, Father Maximilian Hell studied the northern lights between 1767 and 1770, for which he moved to Vardø in the Barents Sea. Although Hell did bring a compass with him, he did not observe any motion of the needle when there was activity and in the end he concluded that the aurora was created by the light of the sun and moon, reflected and refracted by frozen water vapour in the atmosphere. Although this frozen vapour does create interesting effects like “solar pillars,” it is not an explanation for aurorae. 

Start of space physics 

 

Let’s make a jump in time and move towards the twentieth century, with a short stop in 1859. Richard Carrington observed the Sun and made drawings of the sunspots. On 1 September 1859 he noticed a large group of sunspots with bright spots turning into a connecting bright ribbon. This bright ribbon, or solar flare, would create the largest auroral activity in modern times on 2 September of that year: the so-called "Carringtong Event." The northern lights were even seen in the Caribic, telegraph lines stopped working and fire broke out in the stations. Now a solar connection was found: something happened on the Sun and a day later the Earth reacted. This event started the study of the Sun-Earth connection (see “The Sun Kings” by Stuart Clark for the full story) and with that modern space physics.

The idea that there could be a connection between the Earth and the Sun was strange, the distance between the two being so vast. But somehow, when something happens on the Sun the Earth’s magnetic field responds to it. William Herschel e.g. showed that the magnetic disturbances at Earth walked in lockstep with the number of sunspots. 

Kristian Birkeland 

The scientific report of Birkeland's
auroral investigation

Moving back to Scandinavia, to Norway to be specific, we find professor Kristian Birkeland, who was famous for inventing a method to produce saltpeter and for building a hydroelectric plant. This work he did only to finance his studies of the aurora. His was the first extensive study of the aurora, using magnetic field measurements at various locations during "the Norwegian Aurora Polaris Expedition 1902 - 1903." He sent his students and employees to the far north to record magnetic measurements during times of aurora, however he also went himself. Being well aware of Maxwell’s theory of electromagnetism, he knew that if there are deviations in the Earth’s magnetic field, they have to be related to electrical currents. But how exactly does the Sun generate currents in the Earth’s magnetic field?

Birkeland in his laboratory
with the Terrella in action

In order to study the Earth’s magnetic field (and its possible connection to the Sun) Birkeland build a so-called “Terrella” (small Earth) in the laboratory. This terrella consisted of a metal sphere with an electromagnetic inside. This was placed inside a vacuum chamber, the metal sphere was acting as an anode and electrons were emitted from a cathode inside the chamber. When Birkeland turned on the machine, he observed that there were bright rings around the magnetic poles, similar to aurorae. This was an indication for the electic nature of the northern lights.

Based on his experiments with the terrella Birkeland concluded that the aurorae are somehow formed by “solar rays,” particle emissions from the Sun and that: “From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, but of both kinds.“

In other words (as we would say now): the solar wind consists of both negative electrons and positive ions. A bold statement from Birkeland without actual observations of the solar wind.

The solar rays enter into the Earth’s magnetic field; generate the aurora through interaction with the atmosphere; and the magnetic field disturbances through electric currents. How this all worked in detail he could not say, but it seemed to him the most logical explanation.

Unfortunately, the most influential magnetospheric scientist of that time, Sidney Chapman, was not in favour of Birkeland’s hypothesis on the generation of the aurora, and through his influence blocked these ideas from the scientific world. 

Birkeland died in 1917, his ideas about currents in the auroral regions could not be tested by satellite observations until 1963. To read all about Birkeland’s interesting scientific life take a look in “Northern Lights” by Lucy Jago.

In part 2 "From Birkeland to THEMIS"  we will move to 1963 and the space age: did Birkeland get it right?

This story is also available as a lecture:

"Aurora and the Earth's magnetotail: From Birkeland to THEMIS"

Due to lots of traveling I have been unable to keep my promise of a bi-weekly blog post.
The next blog on "magnetotails" will appear soon.
Please be patient, thanks.

JUICE and Ganymede

Last year ESA decided that  JUICE (JUpiter ICy moons Explorer) was going to be the next L-class mission to be build and launched. This was a project long in the making, as I think that in 2002 or 2003 I went to a meeting in France at which a new Jupiter mission was going to be discussed; the name that wast proposed at that time was Laplace. A mission was developed, with the appropriate instrumentation planned.

Then it seemed that the NASA also wanted to send a large mission to Jupiter, so it was set out to make a joined project, two spacecraft that would arrive almost simultaneously at the largest planet of our solar system. First we would have two point measurements and at the end of the ~3 year mission the American satellite would go into orbit around Europa and the European one around Ganymede. The new (strange) name of the mission was EJSM (Europa Jupiter System Mission). However, a financial setback happened at NASA and they withdrew their part of the mission, leaving ESA with the JGO (Jupiter Ganymede Orbiter) which is now called JUICE.

The cover page of the JUICE proposal.

Last month the instrument teams for JUICE were chosen, and fortunately the magnetometer team in which my institute (Space Research Institute, Austrian Academy of Sciences) is involved was selected to fly. Now we just have to build these things and then wait until 2022 when the mission is launched and then wait another 8 years before JUICE arrives at Jupiter. Space physics is nothing for people in a hurry!

The ultimate goal of the mission is the investigation of the Jovian system; atmosphere, magnetosphere, moons, and in the end phase concentrate on the largest moon of the solar system: Ganymede.

Doing science with magnetometers, my main occupation, is more involved than you might think. It is not just measuring the magnetic field and say "okay it's got one", but through careful analysis of the data one can deduce a lot of information, which can come in handy when another instrument is not working, e.g. using waves in the magnetic field you can find out which ion species are present.

In preparation for the final phase of the JUICE mission (you can never be early enough) I decided to use the old Galileo magnetometer data to study this moon's magnetosphere. Early flybys in 1996 had shown that this moon is fully differentiated (i.e. a metal core, rocky mantle and icy shell) and has its own internal magnetic field. This field is strong enough to keep Jupiter's magnetic field at a distance, and thus creates a magnetosphere around Ganymede, similar to the Earth's magnetosphere in the solar wind. In 1997 and 2000 Galileo flew through the upstream magnetosphere (like the dayside of the Earth) and the magnetometer data showed some very interesting details.

A model for field line resonances for the
first (left) and second (right) harmonic,
with the the variations of the electric and
magnetic field shown.

Field line resonances: Magnetic field lines can act like strings on a violin, when you disturb them they start to oscillate with a certain spectrum of distinct frequencies, as shown in the figure. Naturally, one needs to be "on the same field line" to observe this spectrum when the spacecraft passes by. This is a bit easier than it sounds: when the spacecraft remains at basically the same distance of the moon this requirement is fulfilled. This happens for about 3 minutes around closest approach of Galileo to Ganymede. During both flybys such a spectrum was observed at different distances from the moon.

The frequencies of these field line resonances are dependent on the strength of the magnetic field and on the density of the plasma. The first we can measure with our magnetometer, the second we cannot find, because the plasma instrument on Galileo has some problems with the interpretation of the data. Therefore, we compared the observed peaks in the spectrum with a model for a dipole magnetic field and found that the peaks fitted within 5% with those of the model. Thus we could determine the density on the field line. This gave us 2 densities of the plasma in Ganymede's magnetosphere, and as one would expect the flyby that went in deeper measured a higher density. This is similar to the atmosphere of the Earth, where high on a mountain the air is thinner than at sea level.

Ion Cyclotron Waves: When particles get ionized in the presence of a magnetic field then they get "picked up", i.e. they start to gyrate around the magnetic field at a specific gyration period that is determined by the charge and mass of the particle and the strength of the magnetic field. When enough particles are picked up then we can observe waves in the magnetic field data at these specific frequencies. These waves are polarized because the (positive) ions only gyrate clockwise (or left-handed) around the magnetic field whereas electrons gyrate counter-clockwise (or right-handed). Knowing the magnetic field strength, one can search for specific cyclotron frequencies in the spectra of the magnetic field and thereby find out which particles around Ganymede are picked up. With Ganymede's icy surface, it is no wonder that in Galileo's measurements the presence of water-group ions was found. From the amplitude of the waves one can then infer a pickup density, and it was found that, compared to the density of Jupiter's magnetosphere, it was quite high, several times the background density.

If you want to find out all about details (shameless self promotion) you can read it in: Volwerk et al.: ULF waves in Ganymede's upstream magnetosphere published in open access journal Annales Geophysicae.

This was the first of (hopefully) bi-weekly space physics research stories, I hope you enjoyed it. Comments are welcome.

Tusenfem

Revamped

Hi All,

Time for a renewal of 1005 thoughts, only I don't know that I have so many :-)
I  will try to make a Space Physics blog here, with postings on the various space missions that I am working on:

Earth: Cluster, DoubleStar, (THEMIS)
Venus; Venus Express
Jupiter: Galileo, and "soon" JUICE
Saturn: Cassini
Comets: Rosetta

The next post will be about the upcoming mission JUICE and Jupiter's moon Ganymede.

Stay tuned.