
Drinks all round to our friends in India.
India’s Space Research Organisation (ISRO) has successfully docked a pair of satellites, making the nation the fourth to achieve the feat. The Space Docking Experiment (SpaDeX) commenced on December 30, 2024, when India launched a pair of satellites equipped with docking equipment. The mission plan called for the two to be …
There's something I don't get. Two satellites orbiting together with millimeter precision is awesome, but would it not have been simpler to put a disk in front of the one satellite to block the Sun and allow analysis of the corona ?
KISS is still relevant, no ? Especially in space.
We were able to have a telescope deploy itself with vastly more complex requirements, surely a simple disk wouldn't be such an issue ?
The docking attempt was the primary mission and took advantage of that for the the solar observation which seems like a secondary mission. I believe the docking mechanism was based on IDSS which would open the way for docking with ISS or more like Tiangong.
Regardless, great step forward for ISRO.
A disc held on the end of a 150m pole (or even a 150m tall teepee)?
The word "boooiiinngg" springs to mind.
Not to mention the support structure(s) obscuring the view and causing diffraction in the image. Or having the centre of mass moved away from the thrusters on the main body.
And if you're thinking "smaller disc, closer to sensor", then for starters that increases the optical effects of defects on the rim (see diffraction), including weathering (pink, ding).
The requirement for 150m separation for the coronograph is due to diffraction of sunlight around the edge of the occulting disk. The large separation (longer than the nave of the cathedral of Notra Dame in Paris) allows for the corona much closer to the sun's visible surface to be studied.
"In 1931 French astronomer Bernard Lyot – based high in the Pyrenees to observe above the bulk of Earth’s atmosphere – completed the first ‘coronagraph’: a telescope incorporating a disc to occult the Sun, allowing sustained study of the corona.
Driving back waves of light
“This might sound simple, but it’s rendered much harder by the peculiar fact that light acts as both particles and waves,” explains Damien Galano, ESA’s Proba-3 mission manager. “This means some light spills around the edge of whatever’s blocking it, like waves around a seawall. This phenomenon is known as ‘diffraction’; it needs to be designed against to minimise unwanted sunlight reaching your instrument.”
The best way around diffraction is to move an occulting disc further from its telescope. “This is why total solar eclipses give us such an excellent view of the corona, because the Moon is around 384 000 km away from Earth, so diffraction effects are minimal,” explains Andrei Zhukov, Principal Investigator of Proba-3’s main instrument, Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun, ASPIICS."
From: https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3/Eclipse-maker_How_Proba-3_subtracts_the_Sun
Any space structure 150m long (longer than the ISS) would be likely to suffer from vibrations making separate satellites actually the simplest viable solution.
Why is Indian climate expenditure UK taxpayers' problem? There are roughly 40 Indian power stations under construction this year alone while we are closing ours, the Indian population is expected to grow by more than three times our total population in the next 40 years - how good is that for the environment? You could wipe the UK off the face of the earth and the additional environmental damage caused by India alone would completely consume the "saving" in under a decade - and they are nowhere nearly as bad as China.