ALTEA goes to Columbus

18 06 2012

Four (4) hours. Do you know what does it mean to plan a four hour activity on the Space Station? The latest activity with a similar duration was in 2007 and it was the first CNSM measurement on an astronaut. At that time two astronauts were involved and the activity, planned for one hour and half, went well beyond two and a half hours. Just to try to explain what does it mean planning a four hour activity. In a space activity, unexpected issue on a 15 minute activity could cause 3 months of data loss.

Ok, let’s start from the beginning. Who is following ALTEA activities on Twitter (official ALTEA account @ISS_ALTEA) or on Facebook (ALTEA official page) already knows that after being for 6 years inside the UsLab, it was planned to move ALTEA to Columbus in a new configuration.

ALTEA has been in this position in the UsLab since the 22nd of July 2011 (link in Italian), when the Japanese astronaut Satoshi Furukawa moved it from the previous location. At that time the activity was relatively easy, because the particle detectors were already configured on the support structure. All the astronaut had to do was simply to move the whole thing into the new location inside the American module and to start a new measurements.

iss028e018509 (Medium)

Before this activity, it was Paolo Nespoli (link in Italian) who did a great job in assembling the entire detector configuration starting from a dismounted ALTEA in a bag. You can find here the images of that activity. That activity took Paolo more than four hours to complete (can’t remember how long it was planned for), and the activity was only about assembling ALTEA.

This move to Columbus, on the contrary, implied for André to disassemble ALTEA and the support structure completely, put everything in a bag, and then reassemble everything in a new configuration inside Columbus. Let’s consider that the ALTEA Shield support structure is composed by modular plates that need to be assembled just like a jigsaw-puzzle:


This is the configuration assembled by Paolo Nespoli


André Kuipers had to build the configuration named Shield Shield. Four plates have to be assembled in a planar configuration to hold only three SDUs (the particle detectors of ALTEA). Two SDUs are shielded by shielding tiles of different thickness placed above and beyond the particle detector. The third SDU, without shielding, acts as reference. This permits to assess the effectiveness of the shielding by comparing the type and the number of revealed particles.

So it was not an easy task for André, taking into account that he had to move to a different module, on a different pc, with an updated software. The MARS center in Naples who was supporting the operations on our behalf from ground, planned an 8 hour shift to manage possible delay of the activity.

But despite our fears, André completed his activity without any hesitation, without any error, without any issue, and in less than three and a half hours, ALTEA was in Columbus in its new configuration, sending valuable science data to ground.

Here are the pictures of the new configuration:


And after the detectors were inserted in the Columbus racks


Our best congratulations to André for the really good job. And good new measurements to ALTEA.

PS: The PromISSe mission ESA blog talked about ALTEA activity by André.


Here comes the CME. Solar activity update

7 03 2012

The CME that I talked about in Fireworks from the Sun, originated from the X class solar flare of the 5th of March, is hitting the Earth right now. The increasing proton flux has produced an increase of particle flux in the ISS that is being measured by ALTEA. Here is the particle flux detected by ALTEA and the proton flux as detected by GOES satellites.


I remember that you can observe the real time flux as measured by ALTEA with the Integrated Space Weather Analysis System web app.

Let me conclude this flash post with a great infographic on Solar Flares. And stay tuned because a new CME could be arriving in the next days.

See how different types of solar flares stack up in this infographic.
Source: All about our solar system, outer space and exploration

Fireworks from the Sun

7 03 2012

The intense activity of the sun recorded in late February is going on. On 7th of March 2012, the sun unleashed an X5.4-class flare at 00:28 UT coming from Active Region 1429. As described in what is a solar storm? this flare is associated to a large coronal mass ejection (CME) that is not yet known how will impact Earth. After a while a second X5.1 flare happened on the same spot.

An image of the flare as seen by NASA’s Solar Dynamics Observatory (AIA 304)

Below a short video of the double flare.

Download a full sun video of the double flare (ESA HSO movie).

On the same day a CME relative to the 5.1 flare happened on the 5th of March is impacting Earth. On the image below there is the X-Ray flux as measured by GOES satellites where it is possible to see both events.


This is the proton flux as measured by GOES. The sudden increase of flux on the 7th of March is relative to CME related to the flare of March 5th.


And what is the situation of the particle flux inside the ISS? At the moment ALTEA is not seeing any increase of the flux, but I recall you that ALTEA is not very sensitive to protons that are the main component of this kind of events. We will see in next hours since the flux is still increasing. For sure the sun is in a very active period.

Versione italiana: Attività solare. Doppia flare X


iNtegrated Space Weater Analysis System web app

What is a solar storm?

10 02 2012

During the end of January the Sun went through a period of intense activity. The sunspot group 1402 has issued a solar flare with an associated CME that reached the Earth. As we have seen in solar particles these events cause the so-called solar particle events (SPEs). I was invited to speak about the nature of these events and their potential effects on safety for astronauts during the Italian podcast named AstronautiCAST (you can download the episode here). I would like to deepen the topic even here on the blog. We already talked about the solar cycle, sunspots, flares and CME, but how are they correlated and what are their differences?

Let’s start from the structure of the Sun. The Sun is a main sequence star with a mass of 2 × 1030 kg (representing alone 99.8% of the mass of the solar system) essentially made of hydrogen (74%) and helium (25%). Since the Sun doesn’t have a solid surface, but it is in a plasma state, it is subjected to a differential rotation: it rotates faster at the Equator than it does at the poles. The rotation period varies between 25 days of the Equator and 35 of the poles.

The differential rotation of the Sun is at the base of the solar cycle. The solar magnetic field (strongly coupled with the plasma of the photosphere) is warped by the differential rotation and while the solar cycle progresses it is increasingly twisted around the star. During solar minimum the magnetic field configuration is described by phase 1 of the figure, while during solar maximum the magnetic field looks like phase 3.


In this configuration, in which the field is heavily twisted, the field itself can form loops above the photosphere. At the points where the field emerges from the surface it inhibits the heat flow and it produces sunspots, which are colder than normal and are observed in pairs. This process continues until the magnetic dipole is totally destroyed and the polarity of the magnetic field is reversed. For this reason it is more correct to say that the solar cycle lasts 22 years (rather than 11) because this is the time that the magnetic field takes to return to the initial configuration with the Poles not reversed.

This behavior is evident in the following images of quiet Sun and active Sun (false-color image of the radio emission from the Sun’s Very Large Array radio telescope). The most intense points correspond to sunspots (source: NRAO solar radio emission).

These are other pictures where you can clearly see how sunspots show the underlying structure of the magnetic field.


This mosaic of images from NASA’s SOHO footage in extreme ultraviolet (source: shows the connection between solar cycles and sunspot number.

The increased intensity of the solar wind during periods of maximum solar also reduces the flow of galactic cosmic rays with energies below 1 GeV/n.

After seeing what sunspots are, let’s describe the solar flares. The solar flares are huge explosions occurring in the solar atmosphere. The effect of flares is a sudden acceleration of particles, plasma heating up to tens of millions of degrees and the expulsion of huge quantities of solar mass. The flares are classified as A, B, C, M or X depending on their x-ray brightness near the Earth, measured in Watts/m². Each class is ten times more powerful than the previous one, with X (the largest) equal to 1012 W/m² and is divided by 1 to 9 linearly, and then a X2 is four times more powerful than an M5. Solar activity is normally between classes A and C.

There are two main types of flares: impulsive flares and gradual flares.
The impulsive flares mainly accelerate electrons with small amount of protons. Their duration ranges from a few minutes up to a few hours, and the majority comes from regions near the equator.
The gradual flares accelerate protons and nuclei up to speed the coming of light. They occur mainly in regions near the poles.

Below there is the video of the recent January 22 activity. It is very interesting to note how in the region concerned by the flare the magnetic field structure that emerges from the photosphere is clearly visible. In this video, as in other photos, the loops leaving the solar surface are due to the emission of particles of plasma that spiral along the lines of the field, making it visible.


The particles accelerated by flares end up in solar cosmic rays, also known as SEP (solar energetic particles). Solar particle events (SPEs) are defined by the number of protons. Important events show a total proton fluence over 30 MeV greater than 106/cm2. There are about 50 events of this intensity for each solar cycle. Major events have a fluency of protons over 10 MeV greater than 1010/cm2. There are about one or two events of this type for each cycle. Solar particle events associated with flares have up to 30 degree spatial extension.

The CME (coronal mass ejection) are, as the name implies, massive emissions of coronal mass that consists mostly of plasma of protons and electrons. The plasma transported along the magnetic field in the interplanetary space is going to interfere with the planetary magnetic fields encountered along the way. As we already saw, Earth’s magnetic field is deformed by this interaction and a CME can distort it and lower its ability to deflect the cosmic rays (technically, the geomagnetic cutoff is lowered). The energetic particles are also channeled along the field lines reaching low altitudes to form Aurora Borealis. The angular extent of a CME can reach up to 180 degrees sweeping practically half of the plane of the solar system. The speed of propagation of particles of this latest CME was estimated to be 2200 Km/s.

In the following video you can see, at 7th second, the recent CME observed with a coronagraph. Look at the extension of the phenomenon as well as the first relativistic particles that arrive on the sensor of the coronagraph displayed as white streaks.

In the following video, from 00:33 time, a graphical representation of the propagation of a CME in interplanetary space is shown.


Recent studies show that solar flares and CMEs might have a common origin from the phenomenon of magnetic reconnection. Magnetic reconnection is the rearrangement of field lines when two opposing magnetic fields are placed in contact. This rearrangement is accompanied by the sudden release of the energy stored into the two opposing fields.
In the Sun the magnetic field loops that protrude from sunspots can extend over to the point where the lines are reconnected in lower height loops, leaving a magnetic field bubble disconnected from the rest of the loop. The sudden release of energy causes the blasting while the magnetic field and the plasma of protons and electrons contained in the projected bubble expands outwards violently giving rise to CME.

imageimage image

After describing the various physical phenomena that lie behind those commonly known as solar storms, let’s see whether and how these events may be hazardous to the safety of astronauts. While the geomagnetic field protects space crews in LEO orbit from solar events, this protection is not available during an interplanetary trip outside the magnetosphere. The flow of protons during a trip to the Moon or to Mars would be similar to the one measured by geostationary satellites of the GOES series. One of the largest SPE recorded in August 1972 occurred between two missions, Apollo 16 and Apollo 17. If there was an Apollo capsule in a journey to the Moon during this event the astronauts would go through a potentially lethal acute radiation syndrome. During the solar event in October 1989, the Shuttle mission STS-34 was in a slightly tilted (34°) orbit to launch the Galileo spacecraft to Jupiter. Due to the low inclination of the orbit, the protection of the geomagnetic field was enough not to measure any increase in dose during this mission. Meanwhile, aboard the MIR space station, the dosimeter R-16 measured 40 mGy during the events of September and October 1989, equivalent to 100 days of normal exposure on MIR.

I want to end this post with a video responding to various fantasies of conspiracy involving this increased solar activity and the Mayan prophecies about the end of the world in 2012. There are even rumors that NASA has admitted these correlations and has foreseen that during 2012 super solar storms will blow technological civilization away from the face of the Earth. NASA would have also sent an email to employees saying to stay ready.

Here is what NASA thinks: "This solar cycle that will culminate in 2014 isn’t going to be significantly different from the next one, and the next one and the previous one. We always have solar flares. Some times we have big ones, some times we have small ones. Even the most powerful solar event of the last 10000 years could not damage the atmosphere (and the geomagnetic field) so that we are no longer protected. CMEs are happening on the sun all the time and they hit the Earth once or twice a week and in general the effects are minimal. Very powerful ones produce very intense auroras and can have effects on satellites and power grids, but these are the kind of things that people who run these systems know about. And we have warning, since these CMEs can take 2 or 3 days to reach the ground, and we can therefore take appropriate measures to prepare for them. We understand the Sun quite well and we have many spacecrafts that are monitoring it 24 hours a day, 7 days a week, to know that this super storm that is going to wipe out the Earth simply isn’t going to happen."


Sources and further reading:
NASA’S Cosmicopia – Solar activity
Solar Flares and Magnetic Reconnection (ppt)
Observations on Current Sheet and Magnetic Reconnection (ppt)
Space radiation dosimetry in low-Earth orbit and beyond (Benton, 2001)

ALTEA at YRMR 2012 (slides)

23 01 2012

On January 20th I participated to the 3rd Young Researcher Meeting in Rome (read ALTEA at YRMR 2012 (live stream)) with the talk named: "The ALTEA and ALTEA-Shield experiment onboard the International Space Station".

Abstract: Anomalous Long Term Effects in Astronaut’s Central Nervous System (ALTEA) is a helmet-shaped device holding six silicon particle detectors that has been used to measure the effect of the exposure of crewmembers to cosmic radiation on brain activity and visual perception, including astronauts’ perceptions of light flashes behind their eyelids as a result of high-energy radiation. Because of its ability to be operated without a crewmember, it is also being used as a dosimeter to provide quantitative data on high-energy radiation particles passing into the ISS. ALTEA capabilities are also used to give additional information on the exposure of crewmembers to radiation during their stays on ISS for use in health monitoring.
The ALTEA experiment was designed by the Italian Space Agency (ASI) in collaboration with a science team led by Professor L. Narici of Tor Vergata University, Rome. The experiment onboard the International Space Station since July 2006 and it has been used as operative instrument by the Space Radiation Analysis Group (SRAG) of NASA.
Since September 2010 ALTEA detectors are used on a different support for the ESA experiment ALTEA-Shield, which is designed to assess radiation flux in different positions inside the UsLab module. ALTEA-Shield will also provide data about radiation shielding effects by a variety of special materials.
A description of the experiment and a summary of the main results obtained by ALTEA and ALTEA-Shield investigation will be presented.

You can find the slides of the presentation at the following link: (Slides).

If you have any question please feel free to ask with a comment.

Lessons from space

12 01 2012

Expedition 30 crew launched on 22 December from the Baikonur Cosmodrome on a Soyuz spacecraft. The crew is composed by ESA astronaut André Kuipers, Russian cosmonaut Oleg Kononenko and NASA astronaut Don Pettit. They will remain in space for nearly five months as part of the resident, international six-astronaut crew.

During PromISSe long duration mission, André Kuipers will have his eyes on our planet. He will share some of the unique views of Earth from the Station’s Cupola and invite children to become involved in a wide range of educational activities. His observations will support the ESA online lessons designed to help European children strengthen their knowledge in science, technology, engineering and mathematics. These will be part of three themes covering topics such as Life in Space, Biodiversity on Earth and planet Earth’s climate. André will perform experiments on board which can also be carried out by schools. You can follow Andre’s mission here.

Spaceship Earth Theme 1: Life


The first lesson of the Life Theme is about radiation. It gives an overview of different types of radiations and how some forms of radiation pose a threat to astronauts. And talking about cosmic ray effects on astronauts a special mention is dedicated to ALTEA. What is ALTEA? What does it do? and What does ALTEA mean for us? are the questions that this lessons does answer.


You can download this first lesson about radiation here. And of course read all the other lessons. And if you are a student, ask your teachers to download ESA Education kit.

Kit contents:

ISS DVD Lesson 2: Body space
ISS DVD Lesson 3: Space matters
ISS DVD Lessons4: Space robotics
Exploration DVD: The ingredients for Life – on Earth and in Space
Exploration DVD: Feeding our Future – Nutrition on Earth and in Space

Take Your Classroom into Space:
Mass measurement and capillarity
FOAM Stability and Convection
International Space Station Education Kit

What if you are hit by a cosmic ray?

3 01 2012

Cosmic rays are completely ionized atomic nuclei (without any orbiting electrons) that travel through space at very high speed. We already talked about how they are distributed in LEO orbit (as Space Station and Shuttle orbits) where their intensity increases near the magnetic poles and that there is a trapped component of protons in the inner radiation belt that is crossed by LEO orbits in the South Atlantic Anomaly region.

But what happens when cosmic rays go through matter? Ordinary matter is composed by the same nuclei of the cosmic rays, but in this case the electromagnetic strength binds them to their electrons in order to form atoms. The total charge of electrons is equal and opposite to the charge of the corresponding nucleus in order for the atom to be neutral. The nonintutive fact is that ordinary matter is basically empty. If we look at the simplest atom possible, the hydrogen one, we found a single electron orbiting a single proton (in the classic description): the atom dimension is given by the radius of the electron orbit that is 5.3 * 10-11m, while the nucleus, a proton in this case, has a radius of 10-15m.

To understand the relative dimensions, if you imagine the proton as big as a golf ball (that is about 4 cm) the electron would orbit 1 km far away. The proton mass is 200 times the mass of the electron, so for a 1 kg proton the corresponding electron would weight half a gram. Heavier atoms have slightly different ratios, but the orders of magnitudes are similar.

After this check we are entitled to say that matter is empty and mass is enclosed in a very small space (all in nuclei). So whenever a charged particle (from cosmic rays) crosses matter it has much more probabilities to interact with electron distributions than with nuclei themselves. The particle will lose part of its energy during this interaction and its trajectory will be deflected. These two effects are mainly due to

  • anelastic collisions with atomic electrons
  • elastic collisions with nuclei

Less effective processes are

  • Cherenkov radiation emission 
  • nuclear reactions
  • bremsstrahlung

These interactions happens multiple times during the travelling path and their effect cumulate and cause a total energy loss and deflection. The energy loss by impinging particles is transferred to atoms causing their excitation or ionization. The amount of energy transferred in each collision is a very small fraction of the total kinetic energy of the impinging particle. But the number of collisions is so high that even a small thickness causes a considerable energy loss. A 10 MeV proton loses all its energy in 0.25 mm of copper. The high number of interactions in a macroscopic thickness ends up in reduced statistical fluctuations and it permits to define a mean energy loss for lenght unit, that is called stopping power or dE/dx. In the next post I will talk more about mean energy loss, and we will discover which are more dangerous between low or high energy cosmic rays and why it is so difficult to shield from them.