The optical Telescopeelement collects the faint lightwaves of distant stars and galaxies, focusses it into the 3/4 meter secondary mirror and passes it onto the scientific instruments of the ISIM via the fine steering mirror.
With its 18 large hexagonal mirror segments the primary mirror is easily the most prominent feature of the jwst. Each individual mirror is .276m2, making the reflective surface 6,5m2 or about the size of (), and coated with a thin layer of gold, which makes the surface chemically resistant to oxidation and gives the mirror its beatiful shine.
Below the gold is a very light metal called beryllium. beryllium was used, because thermal stability, which means that it does not change shape much when heated or cooled, which is very usefull when considering that the telesope is manufactured at about 20C, but will be used at a -250C. Another property which makes Beryllium stand out in the circumstance is that even tho its very light (it is 1.85 times the density of water, which means that for every gallon of milk, you get almost 2 gallons of beryllium) it is very ridgit and does bend little under stress.
fun fact: beryllium is the 4th element in the periodic table and is used in the 20billion Dollar fusion reactor project currently under construction in france.
Though experiment: think of a magnifying glass and it bourning paper. the Diameter of a magnifying glass is ca. 15cm.
think of the heat and brightness of a magnifying glass the size of large sunshield. think about standing in its beam. not pleasant. it could burn wood, meld metal etc.
the energy received by this sunshield sized magnifying glass focused on the diameter of the secondary mirror would be N. jwst's mirror is n times the size but receives only p times the energy. while on earth a mirror this size could burn metal. in its final orbit, it will receive barely enough energy to heat an egg (?) x degrees C in y Minutes.
? how many rays per second?
even tho the entire telescopes surface is coated in gold, in sum only about 3 grams have been used. that is how thin the layer is. this has been accieved by spraying gold particles instead of using solid gold plates. a wedding ring made of gold weights about n grams, which could coat about n/3 jwsts.
If you where sitting in an oven but wrapped by JWSTs sunshield, you have your oven on full power, but freeze to death.
basically its a tennis court sized umbrella.
as thin as a human hair
made of silicon, aluminum and k****
instruments and telescope operate at -230C to -265C. for this they need be shielded from the sun, earth and moon. also the radiation of other components needs to be blocked.
warm atoms vibrate. the mirror tries to pick up lightwave of soze y. if the mirror was any warmer the vibration of the atoms that made up the mirrow would fuzz the image. mirrors on earth are allways fuzzing, but we dont notice, because the thing hte mirror reflects is very large compared to the fuzz. in a very calm sea, its possible to see the reflection of individual leaves falling of a tree, but when the leave hits the watesurface it causes ripples in the surface (better example water boiling) if the ripples are large enough, it becomes impossible to spot a leave, while the tree is still distinguishable. the leave the jwst tries to spot is a planet on the other side of the universe.
its made of silicone, aluminum and kapton. its basically the wrist cushian material of mousepads spread over aluminum foil.
kapton is used since the 6060s to insulate spacecraft electronis because of its thermoelectric properties.
JWST's orbit is such that at any point in time the sunshield is between the telescope and any heatsource, them beeing sun, earth, moon and JWSTs bus.
The spacecraft BUS is a large thermally insulated box that houses essential spacecraft functionality and is located on the hot side of the sunshield. its about the size of a famillydinnertable but weights as much as 2 baby elephants. inside of it is basically all the technology required to power steer and cool the spacecraft. aswell as the computational processing and storage required by the scientific instruments. thoe bus also houses the antennas nd receives necessary to communicate with its friends at the space telescope science institute in maryland USA.
for its power requirement the JWST uses a 6m long salrarray that sends ca 30v to lithiumIon batteries.
fun fact: the batteries are designed for up to 18000 lifecycles. best my dell can do is 500. take it or leave it.
with a harddrive capacity of 58.9gb, the entire 8 Billion dollar JWST sports about as much stoarge as an entry leve iPhone.
... cpu? battery watts. solar currently
The thermal manageent system is made up of multiple radiators which dissapate heat generated by the instruments (with such elegant names as deployable readiator shade assemblies) and a thick layer of insulation.