Journey to H.E.S.S.

Photo, video & mixed media art

[journeytohess]

Time for vacation in Namibia (/nɑːˈmɪbɪə/). See you in some weeks for a night shift with a H.E.S.S. crew!

< previous     next >

[journeytohess]

One last H.E.S.S. video of the telescopes: awful (real) sound, but beautiful images! When they were moving in your direction to finally point at the place where you were standing, it made a little jolt in the heart :-)  

< previous     next >

[journeytohess]

I can’t stop making pictures of these telescopes! <3 Here is another arty one of #HESSII, with the huge CT5 and the small CT3 (left) and CT2 (right)

< previous     next >

[journeytohess]

Overview* of the H.E.S.S. site

The building of the control room in the forefront and CT1, CT2, CT3, CT4, and the huge CT5 as described. On the right hand side in the back is the building where stood place the inauguration ceremony. And in the front a technical hangar usually used from mounting/fixing the telescopes, it was used during the open day as a small museum where all panels next to the telescopes where shown again but in the shadow :-)

*from a dedicated crane behind the building of the control room, where anybody could go to make nice pictures!

< previous     next >

[journeytohess]

Did you hear that? It is not real! It is a recorded sound of predators to discourage the birds to come close to the telescopes! o_O

< previous     next >

[journeytohess]

Wondering what was in the tree? Look, it is a nest! A nest of sociable weavers (Philetairus socius), a bird endemic to Southern Africa.

Sociable weavers construct permanent nests on trees and other tall objects. These nests are the largest built by any bird, and are large enough to house over a hundred pairs of birds, containing several generations at a time.

< previous     next >

[journeytohess]

Postcard picture of one of the H.E.S.S.I telescopes (CT1)

PS: Did you notice in the tree on the far right?

< previous     next >

[journeytohess]

On the other side of the site, further behind the control room, stands buildings that house several auxiliary systems as well as independent scientific instruments and, in particular, the ATOM telescope.

ATOM is an automatised 75-cm optical telescope. It is a valuable scientific instrument for the H.E.S.S. experiment. It is used mainly for monitoring variable gamma-ray sources and potential H.E.S.S. targets. Besides this task, however, ATOM is also used as a transparency monitor for the atmosphere above H.E.S.S.. It measures atmospheric transmission using stars to help calibrate the Cherenkov shower image analysis.

< previous    next >

[journeytohess]

Aaah that was the way to survive the open day, the heat and the size of the site: biking!

< previous    next >

[journeytohess]

CT5 dancing over the people at the open day

PS: Still no sound on the video. The wind was unbelievable, top on that the noise from the motors of the telescope, trust me you do not want want to hear the result! :-)

< previous    next >

[journeytohess]

So nice to see all these people reaching the H.E.S.S. site in the middle of nowhere for the open-day. and such a diverse public: families with kids, elderly, students from the university of Namibia (UNAM), farmers, backpackers...

< previous     next >

[journeytohess]

From inside the control room: View on the telescopes.

< previous    next >

[journeytohess]

What does CT stand for?

CT stand for Cherenkov Telescope. The Cherenkov light is a faint blue light emitted by the particles of a cosmic shower.

An incident high-energy gamma ray interacts high up in the atmosphere and generates a cosmic shower of secondary particles. The shower particles move at essentially the speed of light, and therefore they emit Cherenkov light, a faint blue light. At 10-km height in the atmosphere, the number of shower particles reaches a maximum, and the shower dies out, only the Cherenkov light goes on to reach the ground.

The Cherenkov light is beamed around the direction of the incident primary particle and illuminates on the ground an area of about 250 m diameter. For example, for a primary photon at TeV energy (1012 eV), only about 100 photons per m2 are seen on the ground. They arrive within a very short time interval of a few nanoseconds.

A telescope located somewhere within the  Cherenkov light will "see" the air shower. The image obtained with the telescope shows the track of the air shower, which points back to the celestial object where there incident gamma ray originated. The intensity of the image is related to the energy of the gamma ray. The shape of the image can be used to reject unwanted "background", such as showers induced by cosmic ray particles.

With a single telescope providing a single view of a shower, it is difficult to reconstruct the exact geometry of the air shower in space. The achieve this, multiple telescopes are used which  view the shower from different points and allow a stereoscopic reconstruction of the shower geometry.

< previous     next >

[journeytohess]

On one the screen in the control room. On this monitor one can always see where the telescopes CT1, CT2, CT3 and CT4 point to, which elevation and which direction they have.

< previous     next >

[journeytohess]

And now the control room! The control room is the place where the telescopes are monitored and where all the measurements are managed from.

< previous     next >

[journeytohess]

More action! Synchronised dance of the huge CT5 with the small CT1 and CT2

< previous     next >

[journeytohess]

Big details of the H.E.S.S. II (CT5) telescopes

Top-left, is the H.E.S.S. II telescope (CT5). CT5 is 28-m high, while the first four telescopes were only 12 m. CT5 weighs 580 tons and is ten times more massive than the smaller ones.

One can see in the top-right of the dish that a mirror is missing. It is actually another camera (”sky CDD”). With this camera, one can check the exact position of the telescope. This camera watch the stars, therefore one can correct the position of the telescope according to the position of the stars in the (night) sky.

Midlle right hand side, in the centre of the dish stands a laser light pulser, which illuminates the camera uniformly and is used to flat-field the camera. There is also a "lid CCD" mounted in the centre of the dish, viewing the camera. The lid CDD is used to align mirrors and to monitor the point spread function by viewing the images of stars on the white camera lid, and to monitor deformations of the camera masts under gravity by viewing reference LEDs on the camera body.

Midlle right hand side is the camera. The H.E.S.S. II camera follows the design of the H.E.S.S. I cameras: Photomultiplier tubes are group into 16-PMT drawers which also contain the electronics for signal storage, signal digitization, triggering and readout. However, the H.E.S.S. II camera is much larger - it contains 2048 PMTs in 128 drawers.

Bottom picture is one boogie of CT5. CT5 can rotate on a 36-m diameter rail thanks to its 12 wheels in 6 bogies. Only 4 wheels are driven by motors. The peak positioning speed is 200 degr./minute within a range +– 280 degr. from park position.

On the H.E.S.S. website can be found detailed Information about of the H.E.S.S. telescopes and comparison of parameters of two kinds of telescopes.

< previous     next >