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Optical stabilising reference cavity
30-11-2016 04:03 PM CET

europeanspaceagency posted a photo:

Optical stabilising reference cavity

What looks like an abstract sculpture is actually the laser equivalent of a tuning fork – to serve a new generation of space instruments.

“This is an ‘optical stabilising reference cavity’, through which laser light is contained between a pair of super-polished mirrors kept a precise distance apart,” explains ESA physicist Eamonn Murphy.

”This laser light is then used to lock the frequency of the laser – and prevent it drifting – in a similar principle to a tuning fork, as applied to musical instruments.”

Such lasers will serve at the heart of next-generation ‘optical atomic clocks’, improving on current microwave atomic clocks used for timing and navigation, as well as enabling ultrasensitive gravity detectors.

This 5 cm cube cavity was developed for ESA by the National Physical Laboratory, NPL, which is the national measurement institute of the UK, specialised in extremely precise measuring techniques.

NPL used ultra-low expansion glass, resistant to changing size with temperature. A pathway was then drilled through the middle, with mirrors placed at either end.

The working version of the cavity is enclosed in a vacuum chamber to prevent any disturbance by air molecules, followed by a thermal shroud to maintain its temperature to within a tiny fraction of a degree. It can then be placed on an acoustic damping baseplate to further isolate it from any microvibrations.

This effort began back in 2009 with three parallel projects within ESA’s Basic Technology Research Programme, working with the national measuring institutes France and Germany as well as the UK.

Expertise and elements from all the resulting designs will soon be incorporated into a new working prototype, supported through ESA’s General Support Technology Programme, which finalises hardware for space.

“Our aim is to deliver a six order-of-magnitude improvement in laser linewidth from initial laser performance,” adds Eamonn, “to maintain a stable drift-free frequency, insensitive to even minute accelerations.”

Credit: NPL

Mares machine
30-11-2016 11:13 AM CET

europeanspaceagency posted a photo:

Mares machine

The Muscle Atrophy Research and Exercise System, or Mares for short, is a three-in-one muscle-measurement machine on the International Space Station to monitor astronauts’ muscles as they work out.

Muscle strength drops during spaceflight and researchers need to know why this happens in order to prepare for long missions and safe space tourism. Mares is an exercise bench that offers detailed information about how muscles behave in space.

Looking at muscle contraction at a single moment gives little information but Mares provides a full overview of muscle speed and force as an elbow or knee joint bends.

Our bodies are amazing machines that perform wonderful feats daily without us even noticing. Hold a glass in your hand and fill it with water and your arm muscles will automatically hold the glass steady and stable despite the changing weight as it fills.

Mares can chart this fine motor control as well as give a precise overview of muscle torque and speed. Astronauts move their joints to follow a graph or dot on a screen as a motor generates counterforce.

This week, ESA astronaut Thomas Pesquet is installing the machine in Europe’s Columbus space laboratory and he will be the first test subject for researchers on Earth. Thomas’ fellow ESA astronauts Andreas Mogensen, Samantha Cristoforetti and Tim Peake, tested the machine to make sure it works correctly ready for use.

Thomas is one week into his six-month Proxima mission on the International Space Station. Follow him and his adventure in space via thomaspesquet.esa.int

Credit: ESA/NASA

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