ESA: Pioneering Cluster mission is celebrating its 10th

[bystander]

ESA’s pioneering Cluster mission is celebrating its 10th anniversary
European Space Agency | Space Science | 25 Aug 2010

Media representatives are cordially invited to a briefing on the occasion of ten years of scientific discoveries by ESA’s Cluster mission.

Over the past decade, Cluster’s four satellites have provided extraordinary insights into the largely invisible interaction between the Sun and Earth. The media briefing takes place at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, on 1 September 2010 from 11:00 – 12:00 am. Doors open at 10:30 am.

ESA mission scientists and operations managers will present the latest and most important scientific results of Cluster and explain the operational challenges it has had to face during ten years of formation flight. A constellation of four spacecraft flying in formation around Earth since 1 September 2000, Cluster has been making the most detailed investigation ever of the interaction between the solar wind and Earth’s protective magnetic field, depicting it in three dimensions.

The solar wind is a hot, thin, electrically charged gas continuously ejected by the Sun. Depending on the intensity of the magnetic activity of the Sun, the solar wind can transform into a violent solar storm. Among other results, Cluster has shown how the solar wind particles break through the protective magnetic shield hitting Earth’s atmosphere. During critical space weather conditions, solar storms can lead to disruption of communication, computers, power supplies and navigation systems on Earth.

Cluster has now spent a decade passing in and out of our planet's magnetic field, returning invaluable data. New observations, made when Cluster recently crossed the heart of the auroral acceleration region, will also be presented.

For more detailed information on the Cluster mission: http://sci.esa.int/cluster

Ten Years Flying in Formation: The Legendary Cluster Quartet
Science Daily | 27 Aug 2010

Cluster mounted on Soyuz - 12 Jul 2000. [i](Credit: ESA)[/i]

---

Next week marks the 10th anniversary of the start of formation flying for the four satellites of ESA's Cluster quartet, one of the most successful scientific missions ever launched.

On 1 September 2000, just a few weeks after launch, the four individual satellites of the Cluster mission began coordinated orbits, marking the formal start of formation flying.

Since then, the four satellites -- dubbed Samba, Tango, Rumba and Salsa -- have gone on to collect some of the most detailed data ever on the physical properties of space between Earth and the Sun, and on the interactions between the charged particles of the solar wind and Earth's atmosphere. In all, over 2.6 terabytes of data -- enough to fill 3300 CDROMS -- have been delivered from space.

The Cluster mission was lofted into orbit in two dual launches on Soyuz boosters from Baikonur Cosmodrome, Kazakhstan, on 16 July and 9 August 2000.

[bystander]

Cluster turns the invisible into the visible
European Space Agency | 01 Sep 2010

Cluster has spent a decade revealing previously hidden interactions between the Sun and Earth. Its studies have uncovered secrets of aurora, solar storms, and given us insight into fundamental processes that occur across the Universe. And there is more work to do.

The aurora, those dancing lights in the polar skies, are but the visible manifestation of an invisible battle taking place above our heads. Supersonic particles from the Sun collide with our planet’s magnetic field every day. Most are deflected away but some are trapped by Earth’s magnetism and accelerated to collide with the atmosphere, creating the aurora, the planet’s radiation belts and from time to time large magnetic storms worldwide.

In its decade studying this activity, Cluster has discovered giant magnetic whirlpools injecting new particles into Earth’s field, huge ‘holes’ in the uppermost atmosphere of Earth that create black regions in the visible aurora, and magnetic dead spots called nulls that form just as the magnetic landscape of space is about to snap into a new configuration.
...
There is a global science community working on Cluster. Every other day, a science team somewhere in the world has a paper accepted for publication that relies on Cluster data. The Cluster Active Archive already possesses more than 1000 users worldwide, ensuring that the science results will continue even after the mission itself comes to an end.

Ten years is a long time in the severe condition of space. The four Cluster spacecraft are all showing their age and the operations team face a daily challenge to keep the fleet operational. Perhaps the biggest task is to make sure the power keep flowing.

The solar panels no longer generate as much electricity as they did, and the batteries onboard are gradually breaking down in a dramatic way: a series of minor explosions. The batteries are made of non-magnetic silver-cadmium to avoid interfering with Cluster’s instruments. But over time, such batteries generate oxyhydrogen, an explosive gas. To date seven batteries have cracked across the four spacecraft, two of which were more like small explosions. Ground controllers saw the spacecraft lurch each time this happened. From twenty batteries, just nine remain. Yet new, creative scenarios for operations mean the spacecraft remain almost fully functional despite the loss of battery power.

And there is a lot still to be done. Recently, Cluster’s approach to Earth was lowered from 19 000 km to just several hundred kilometres. This will sweep Cluster through the regions responsible for the final acceleration of auroral particles, giving scientists an unparalleled view of this behaviour.

Whilst Cluster is firmly in orbit around the Earth, its science is fundamental to our understanding of the most distant realms of the Universe.
...
Cluster is expected to operate until 2012. A mission extension is under review to extend its operations to 2014.

[neufer]

Cluster turns the invisible into the visible
European Space Agency | 01 Sep 2010

The four Cluster spacecraft [Samba, Tango, Rumba & Salsa] are all showing their age and the operations team face a daily challenge to keep the fleet operational. Perhaps the biggest task is to make sure the power keep flowing. The solar panels no longer generate as much electricity as they did, and the batteries onboard are gradually breaking down in a dramatic way: a series of minor explosions. The batteries are made of non-magnetic silver-cadmium to avoid interfering with Cluster’s instruments. But over time, such batteries generate oxyhydrogen, an explosive gas. To date seven batteries have cracked across the four spacecraft, two of which were more like small explosions. Ground controllers saw the spacecraft lurch each time this happened. From twenty batteries, just nine remain. Yet new, creative scenarios for operations mean the spacecraft remain almost fully functional despite the loss of battery power.

And there is a lot still to be done. Recently, Cluster’s approach to Earth was lowered from 19 000 km to just several hundred kilometres. This will sweep Cluster through the regions responsible for the final acceleration of auroral particles, giving scientists an unparalleled view of this behaviour. Cluster is expected to operate until 2012.

<<Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases, typically in a 2:1 molar ratio, the same proportion as water. This gaseous mixture is used for torches for the processing of refractory materials and was the first gaseous mixture used for welding. In practice a ratio of 4:1 or 5:1 hydrogen:oxygen is required to avoid an oxidizing flame.

Oxyhydrogen will combust when brought to its autoignition temperature. For a stoichiometric mixture at normal atmospheric pressure, autoignition occurs at about 570 °C. When ignited, the gas mixture converts to water vapor. The maximum temperature of about 2800 °C is achieved with a pure stoichiometric mixture, about 700 degrees hotter than a hydrogen flame in air.

Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. Due to competition from the acetylene-fueled cutting torch and from arc welding, the oxyhydrogen torch is seldom used today.>>

[Beyond]

<<Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases, typically in a 2:1 molar ratio, the same proportion as water. This gaseous mixture is used for torches for the processing of refractory materials and was the first gaseous mixture used for welding. In practice a ratio of 4:1 or 5:1 hydrogen:oxygen is required to avoid an oxidizing flame.

Oxyhydrogen will combust when brought to its autoignition temperature. For a stoichiometric mixture at normal atmospheric pressure, autoignition occurs at about 570 °C. When ignited, the gas mixture converts to water vapor. The maximum temperature of about 2800 °C is achieved with a pure stoichiometric mixture, about 700 degrees hotter than a hydrogen flame in air.

Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence. Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. Due to competition from the acetylene-fueled cutting torch and from arc welding, the oxyhydrogen torch is seldom used today.>>

Not being a rocket scientist i may be a bit off or confused, but H2-O2 is hydrogen peroxide, is it not? So if i go to a store and get some regular-good ole' hydrogen peroxide and heat it to about 920 F, it will go "BOOM"?

[neufer]

<<Not being a rocket scientist i may be a bit off or confused, but H2-O2 is hydrogen peroxide, is it not? So if i go to a store and get some regular-good ole' hydrogen peroxide and heat it to about 920 F, it will go "BOOM"?>>

It sounds like a fascinating experiment, beyond. Go for it

[Oxymoron is a mixture of a moron (Me₂) and molecular oxygen (O₂), usually in a 2:1 Holy roller ratio.]

[bystander]

Not being a rocket scientist i may be a bit off or confused, but H2-O2 is hydrogen peroxide, is it not? So if i go to a store and get some regular-good ole' hydrogen peroxide and heat it to about 920 F, it will go "BOOM"?

H₂O₂ is indeed hydrogen peroxide, which can be used as a propellant, usually by decomposition into steam and oxygen (2·H₂O₂ → 2·H₂O + O₂).

Oxyhydrogen is a mixture of molecular hydrogen (H₂) and molecular oxygen (O₂), usually in a 2:1 molar ratio (2·H₂ : O₂). Some of the mixture may combine into H₂O₂ and/or H₂O, but most of it will remain as molecular hydrogen and oxygen.

[Beyond]

Not being a rocket scientist i may be a bit off or confused, but H2-O2 is hydrogen peroxide, is it not? So if i go to a store and get some regular-good ole' hydrogen peroxide and heat it to about 920 F, it will go "BOOM"?

H₂O₂ is indeed hydrogen peroxide, which can be used as a propellant, usually by decomposition into steam and oxygen (2·H₂O₂ → 2·H₂O + O₂).

Oxyhydrogen is a mixture of molecular hydrogen (H₂) and molecular oxygen (O₂), usually in a 2:1 molar ratio (2·H₂ : O₂). Some of the mixture may combine into H₂O₂ and/or H₂O, but most of it will remain as molecular hydrogen and oxygen.

So then....hydrogen peroxide is when hydrogen and oxygen are combined and then burned; and the molecular hydrogen and oxygen remain separate until they come together to be burned? Or are the moleculars used for fuel at all??

[bystander]

So then....hydrogen peroxide is when hydrogen and oxygen are combined and then burned; and the molecular hydrogen and oxygen remain separate until they come together to be burned? Or are the moleculars used for fuel at all??

Hydrogen is a very efficient and evironmentally friendly fuel. When Hydrogen is burned with Oxygen, the result is water. Some oxidizing agent is required to burn anything. Hydrogen Peroxide may be used as an oxidizer, but is probably more effective as a monopropellant where it is decomposed into water and oxygen.

H₂O₂ is not the same as H₂ O₂. H₂O₂ is the chemical symbol for hydrogen peroxide, much the same as H₂O is the symbol for water. H₂ is molecular hydrogen and O₂ is molecular oxygen. They are the most common forms of hydrogen and oxygen found on Earth. They are very rare in atomic form (H and O) because both are highly reactive.

[neufer]

Astrogeologist Gene Shoemaker wearing a H[sub]2[/sub]O[sub]2[/sub] Bell Rocket Belt while training astronauts.

---

<<High concentration H₂O₂ is referred to as HTP or High test peroxide. It can be used either as a monopropellant (not mixed with fuel) or as the oxidizer component of a bipropellant rocket. Use as a monopropellant takes advantage of the decomposition of 70–98+% concentration hydrogen peroxide into steam and oxygen. The propellant is pumped into a reaction chamber where a catalyst, usually a silver or platinum screen, triggers decomposition, producing steam at over 600 °C, which is expelled through a nozzle, generating thrust. H₂O₂ monopropellant produces a maximum specific impulse (Isp) of 161 s (1.6 kN·s/kg), which makes it a low-performance monopropellant. Peroxide generates much less thrust than hydrazine, but is not toxic. The Bell Rocket Belt used hydrogen peroxide monopropellant.

As a bipropellant H₂O₂ is decomposed to burn a fuel as an oxidizer. Specific impulses as high as 350 s (3.5 kN·s/kg) can be achieved, depending on the fuel. Peroxide used as an oxidizer gives a somewhat lower Isp than liquid oxygen, but is dense, storable, noncryogenic and can be more easily used to drive gas turbines to give high pressures using an efficient closed cycle. It can also be used for regenerative cooling of rocket engines. Peroxide was used very successfully as an oxidizer in World-War-II German rockets (e.g. for the Me-163), and for the low-cost British Black Knight and Black Arrow launchers.

In the 1940s and 1950s, the Walter turbine used hydrogen peroxide for use in submarines while submerged; it was found to be too noisy and require too much maintenance compared to diesel-electric power systems. Some torpedoes used hydrogen peroxide as oxidizer or propellant, but this was dangerous and has been discontinued by most navies. Hydrogen peroxide leaks were blamed for the sinkings of HMS Sidon and the Russian submarine Kursk. It was discovered, for example, by the Japanese Navy in torpedo trials, that the concentration of H₂O₂ in right-angle bends in HTP pipework can often lead to explosions in submarines and torpedoes. SAAB Underwater Systems is manufacturing the Torpedo 2000. This torpedo, used by the Swedish navy, is powered by a piston engine propelled by HTP as an oxidizer and kerosene as a fuel in a bipropellant system.

While rarely used now as a monopropellant for large engines, small hydrogen peroxide attitude control thrusters are still in use on some satellites. They are easy to throttle, and safer to fuel and handle before launch than hydrazine thrusters. However, hydrazine is more often used in spacecraft because of its higher specific impulse and lower rate of decomposition.

[bystander]

Cluster Helps Disentangle Turbulence in the Solar Wind
NASA GSFC | 04 Oct 2010

From Earth, the Sun looks like a calm, placid body that does little more than shine brightly while marching across the sky. Images from a bit closer, of course, show it’s an unruly ball of hot gas that can expel long plumes out into space – but even this isn’t the whole story. Surrounding the Sun is a roiling wind of electrons and protons that shows constant turbulence at every size scale: long streaming jets, smaller whirling eddies, and even microscopic movements as charged particles circle in miniature orbits. Through it all, great magnetic waves and electric currents move through, stirring up the particles even more.

This solar wind is some million degrees Celsius, can move as fast as 750 kilometers (466 statute miles) per second, and – so far – defies a complete description by any one theory. It’s hotter than expected, for one, and no one has yet agreed which of several theories offers the best explanation.

Now, the ESA/NASA Cluster mission – four identical spacecraft that fly in a tight formation to provide 3-dimensional snapshots of structures around Earth – has provided new information about how the protons in the solar wind are heated.
...
Scientists know that large turbulence tends to “cascade” down into smaller turbulence -- imagine the sharply defined whitecaps on top of long ocean waves. In ocean waves, the energy from such cascades naturally adds a small amount of heat from friction as the particles shift past each other, thus heating the water slightly. But the fast, charged particles – known as “plasma” -- around the sun don’t experience that kind of friction, yet they heat up in a similar way.
...
Somehow the magnetic and electric fields in the plasma must contribute to heating the particles. Decades of research on the solar wind have been able to infer the length and effects of the magnetic waves, but direct observation was not possible before the Cluster mission watched large waves from afar. These start long as long wavelength fluctuations, but lose energy – while getting shorter – over time. Loss of energy in the waves transfer energy to the solar wind particles, heating them up, but the exact method of energy transfer, and the exact nature of the waves doing the heating, has not been completely established.

In addition to trying to find the mechanism that heats the solar wind, there’s another mystery: The magnetic waves transfer heat to the particles at different rates depending on their wavelength. The largest waves lose energy at a continuous rate until they make it down to about 100-kilometer wavelength. They then lose energy even more quickly before they hit around 2-kilometer wavelength and return to more or less the previous rate. To tackle these puzzles, scientists used data from Cluster when it was in the solar wind in a position where it could not be influenced by Earth’s magnetosphere.

For this latest paper, the four Cluster spacecraft provided 50 minutes of data at a time when conditions were just right -- the spacecraft were in a homogeneous area of the solar wind, they were close together, and they formed a perfect tetrahedral shape -- such that the instruments could measure electromagnetic waves in three dimensions at the small scales that affect protons.

The measurements showed that the cascade of turbulence occurs through the action of a special kind of traveling waves – named Alfvén waves after Nobel laureate Hannes Alfvén, who discovered them in 1941.

The surprising thing about the waves that Cluster observed is that they pointed perpendicular to the magnetic field. This is in contrast to previous work from the Helios spacecraft, which in the 1970’s examined magnetic waves closer to the sun. That work found magnetic waves running parallel to the magnetic field, which can send particles moving in tight circular orbits – a process known as cyclotron resonance -- thus giving them a kick in both energy and temperature. The perpendicular waves found here, on the other hand, create electric fields that efficiently transfer energy to particles by, essentially, pushing them to move faster.

Indeed, earlier Cluster work suggested that this process – known as Landau damping – helped heat electrons. But, since much of the change in temperature with distance from the sun is due to changes in the proton temperature, it was crucial to understand how they obtained their energy. Since hot electrons do not heat protons very well at all, this couldn’t be the mechanism.

That Landau damping is what adds energy to both protons and electrons – at least near Earth – also helps explain the odd rate change in wave fluctuations as well. When the wavelengths are about 100 kilometers or a bit shorter, the electric fields of these perpendicular waves heat protons very efficiently. So, at these lengths, the waves transfer energy quickly to the surrounding protons -- offering an explanation why the magnetic waves suddenly begin to lose energy at a faster rate. Waves that are about two kilometers, however, do not interact efficiently with protons because the electric fields oscillate too fast to push them. Instead these shorter waves begin to push and heat electrons efficiently and quickly deplete all the energy in the waves.

Three Dimensional Anisotropic k Spectra of Turbulence at Subproton Scales in the Solar Wind F Sahraoui et al

• Physical Review Letters 105 131101 (23 Sep 2010) DOI: 10.1103/PhysRevLett.105.131101