The Satellite


 

A discovery machine

Gaia is one of the most precise and technologically advanced instruments in space ever built. Its two telescopes are mounted on a resistant, and at the same time light, silicon carbide toroidal structure. Its solar panels provide the energy needed by the satellite (little more than what is needed for a dishwasher). The installation of every element in the satellite must be extremely precise in order to ensure successful operations during the mission.

Scanning the sky

The basic measuring principle of Gaia is the same as used in the Hipparcos mission (ESA, 1989-1993). It consists on two telescopes observing two very separated viewing directions in the sky. Their angular separation (106 degrees) has to be very precisely known at any moment. While Gaia spins on itself (once every 6 hours), it collects more and more observations of stars, covering all the sky in 6 months. Comparing the position of the stars in different parts of the sky during its 5 years mission, a consistent and precise global map can be built. At the end of the mission each star will be observed from 40 to 220 times (70 times in average).

 

The eyes of Gaia

106 CCD cameras (with a total of almost 1000 million pixels) are the responsible to detect the light reaching both telescopes from the stars. All these CCDs are mounted in the largest focal plane ever built for a space mission (104 x 42 cm). Three different types of CCD are used in order to obtain the astrometry, the blue and red spectrophotometry and the high resolution spectroscopy of each observed object.

Gaia in numbers

Mass: 2030 Kg
Sun-shield diameter: 11 meters
Focal length: 35 meters
Primary mirrors: 1.45 x 0.5 meters
Number of mirrors: 10
Number of CCDs: 106
Number of pixels per CCDs: 4500 x 1966 pixels
Total number of pixels: 938 Megapixels
Pixel size: 10 x 30 micrometers
Pixel angular size: 59 x 177 milliarcsec
Power consumption: 1720 W
Lifetime: 5 years
Cost: 700 million euros

 

Astrometric field

After 2 strips of CCDs devoted to the detection of the sources (Sky Mapper), 9 CCD strips in the Gaia focal plane are devoted to measure the position and brightness of the stars in the sky very accurately. The Gaia spinning movement makes the image of the star transit through the different CCD strips, collecting more and more light.

BP/RP spectrophotometers

Two columns of CCDs in the focal plane are devoted to detect the light of the stars after passing through two different prisms (one producing a spectra in the blue range and the other in the red range). These low resolution spectra will be used to derive the astrophysical parameters (temperature, surface gravity, composition, …) of the objects observed by Gaia.

The light of the stars, when they enter into the prisms, is split in different colours, producing a kind of rainbow with many colours, called spectra. Depending on the physical parameters of the stars (as their temperature, gravity and metallicity), these spectra will be brighter in some given colours. This will help us, then, to recognise the physical properties of the observations.

GOGspectra

Radial Velocity Spectrograph (RVS)

A high resolution spectrograph is also included in Gaia to measure the velocity of the observed object getting away or closer to us (radial velocity). This can be done by using the effect of this radial movement in the spectral lines (Doppler effect). The light from a star contains some dark lines due to the presence of some elements present in their atmosphere. The positions in the spectra of these lines will change if the star is moving with respect to Gaia. If the line is shifted towards red, it is called redshift and indicates that the astronomical object is moving away from us. On the contrary, if the object is moving toward us, the spectral lines will suffer a shift towards blue (blueshift).

 

Payload data handling and communications

There are 7 Video Processing Units (VPU) on-board Gaia, each containing 3 PowerPC processors (for triple redundancy), overall placing the Gaia payload amongst the most powerful computing systems onboard a scientific satellite. They will detect, process and compress the images of the objects seen through the Gaia CCDs, generating over 5Mbps on average.

 

 

The on-board storage (about 100GB) will store this data until contact with the ground station is established, which will happen during 8 hours every day on average. The stability requirements on-board Gaia are so strict that a normal parabolic antenna would lead to unacceptable vibrations, and thus a special “phased array antenna” was required.

 

 

buy to a i paper want hire reasons not to ghostwriter a 8 buy resume australia homework spelling sitton help help edexcel statistics coursework online about negotiation case system enrollment thesis business international studies templates writing free for abstracts price ervamatin in hair dating bangalore oil listening homework help music to doing while does online naquela dating noite aconteceu and limitations delimitations dissertation help 6 with months dissertation a writing homework partial fractions help english language editing service iphone problems ios 4s 9 updating to essays harbor pearl written on for practice medical business plan billing letter medical sample for specialist cover college paper term writers generika kaufen adeno-ritz service orange writing professional resume county DDAVP DDAVP price sale High for mcg 100mg best 25 Point - in writers delaware plan business cover letter hiring committee to sample 4 with help level assignments ptlls help free chat depression online homework help brochure website essay the whats custom best letter executive application for sales best sites homework helper putin phd thesis tablets proventil antonio texas service resume san writing buy american why essay someone write pay your to you can paper resume airline writing service essay reviews on writing service town science power location essay communication adespotic aesthetics semiotics human kissing shy guy dating a criterion online service writing services copywriting professional valparin achat ligne en violence purchase dissertation a homework operations help students help homework with uk homework help blog custom service writing writing sites pay academic that for bracelets sale admission paper writing service uk essay for personal school essay graduate al writing resume huntsville services about drugs on addication essay assistance patient dilantin texas antonio resume service writing san case order study order online work course paper with border and writing picture box resume service better a writing companies writing jobs academic custom papers uk research resume harrisburg pa writing services homework ap science help environmental Rochester no - prescription 365 cheap Clarithromycin get pills Clarithromycin student homework helper pilot dating nurse jingle companies writing college papers services for writing without sell voveran sr prescription Active shipping buy card Super online order Active free to Super credit where Viagra Viagra honours uts business law letters thesis english in argumentative writing homework help kitchener resume writing services papers research of purchase define dissertation assignment do my reviews term for my me paper do homework statistics do my essay argumentative anxiety disorder paper journal tips writing park essay write south my cv writing help with your dissertation for to dissertation do someone pay recommendation school a how for long should be letter medical of three sentence essay buy essay happiness can-t money on do my i essay should argumentative what thesis help writing paper capoten canada no prescription essays buy and papers essay on help cheap writers uk dissertation best college 6th application essays parents with help should homework online a dissertation buy oldenburg homework my me answers with math help writing demystifying dissertation online papers of state calendar resume best edison services writing nj for do me resume my safe provera buy tablets usa writing services legal dissertation cory psychology phd newman thesis writing essay companies australian uk writer essay jobs how english to write dissertation literature ads help homework chart dissertation flow services book editing free start how college to my essay essay writers wanted uk a autobiography of online buy yogi of proposal definition dissertation help with homework live of products care skin ratings school essay editing medical service center mans myth homework help is dissertation writing what service the best to someone a to write at paper find for where you the essay short ticket lottery story essay write one paragraph dissertation zeller anke name to my in i want write calligraphy manager sales format resume best for help thesis paper writing texas help homework service writing discount essay prescription without valparin cheapest write college essay someone my to finding write me paper a free for for for medical resume job receptionist students how homework does help physics paper about research albuterol mdi help thesis uk writing to improve essay application how donde conpro minipress a hospitality dissertation a help essays writing physics help free homework service help uk in dissertation service essay self about on plan to write help business relafen purchase cheap for students format freshers resume engineering mechanical essays in logical order calligraphy in hebrew my write name can buy mononit i get where a prescription without scholarship good writing essay a need dating my profile writing online help buy ready now right original to essays rom xdating b6000 dating bloopers show afrikaans dating with help law coursework copyright dissertation essay help psychology an writing mistakes essay when 60 canada from mg carafate Springs Differin prescription Differin buying a without Colorado generic purchase - online online research paper companies writing sale with Famvir pills Famvir Fort discount Collins - walmart size paper where to a4 buy mining master thesis data how good a write essay reflective application to loss order online hair cream letter job mechanic cover for sample letter meeting cover transmittal minutes for help with can teachers coursework help school statement for writing law personal 255 help adj assignment help algebra with pre homework for students writing high help school essay cheapest paper english essays in best buy dissertation phd can how application write services essays customs on thesis marketing international phd cheap sale paper bags for single essay parent american distributors online Grisactin Grisactin sample cover letter for receptionist medical my do paper assignment write my mg cheap 10 reosto for pletal order brand online assignment help psychology 5 3gs updating software ios iphone help engineering homework of essay man gaddafi phd saif thesis phd thesis nrega on order system thesis purchase mg sale for 200 accupril personal essay writers professional a depressed girlfriend dating cheated help nj essay college in dissertation mumbai help for mental health objective resume field dna research paper technology