ESA satellites to test razor-sharp formation flying
spectrum.ieee.org
spectrum.ieee.org
Just recently, we completed a series of correction burns to match the semi-major axis of the orbit of both satellites to stop them drifting away from each other. In a few weeks/months we'll bring them back together and send a software update that will allow them to autonomously maintain formation flight.
Also, we will be doing live satellite operations at the Lange Nacht der Wissenschaften (22. June 2024) :)
Does it feel as cool as one would imagine?
It's not quite my first rodeo with this stuff, but it's still incredible to be a part of and see.
[It's incredible to be a part of, but it's also just a whole lot of attention to detail, paperwork, and paranoia]
People don't tend to let HS students do much, so it's pretty stirring when they get an email that said approximately "We appreciate your... dedication to furthering humanity’s presence in space and knowledge of the cosmos."
I can only imagine how cool it must feel to be part of a project that has escaped the Earth's atmosphere, and zips by at orbital speeds. I would think that those high school kids will benefit from this project a lot. A truly mind-expanding experience.
> That brings us to GRACE—a backronym for gravity recovery and climate experiment—a pair of satellites that orbited the Earth at a fixed distance from each other. Or they would be fixed if the Earth’s gravity didn’t change in time and space. GRACE used a radar system to measure the distance between the two satellites to track those changes, providing information about the gravitational field it was traveling through.
* https://arstechnica.com/science/2019/07/satellites-play-chas...
https://en.wikipedia.org/wiki/Space_Interferometry_Mission?w...
https://en.wikipedia.org/wiki/LISA_Pathfinder ("LISA Pathfinder")
I wonder how precisely they can control the relative separation of those interferometer spacecraft? (They advertise they can measure the separation to <0.01 nanometers—but that's not quite the same thing).
Probably more a matter of precisely measuring the gravitational fields and accounting for those than of controlling their relative position extremely precisely (besides of course the precision needed to target the lasers across such a large distance).
"And what does that mean to you?"
"It means someone really wanted our initials to spell out "S.H.I.E.L.D."
Ba-dump-tish.
> A backronym is an acronym formed from an already existing word by expanding its letters into the words of a phrase. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology. The word is a portmanteau of back and acronym.[1]
> A normal acronym is a word derived from the initial letters of the words of a phrase,[2] such as radar from "radio detection and ranging".[3] By contrast, a backronym is "an acronym deliberately formed from a phrase whose initial letters spell out a particular word or words, either to create a memorable name or as a fanciful explanation of a word's origin."[1] Many fictional espionage organizations are backronyms, such as SPECTRE (special executive for counterintelligence, terrorism, revenge and extortion) from the James Bond franchise.
> For example, the Amber Alert missing-child program was named after Amber Hagerman, a nine-year-old girl who was abducted and murdered in 1996.[4] Officials later publicized the backronym "America's Missing: Broadcast Emergency Response".[5]
If there's any questions, I might be able to give some answers. However, I'm not involved with Proba-3 directly, so no guarantees.
For Proba-3 the goal is to have the two satellites more than 100m apart. If you want to do that with a stick, your stick has to be longer than the ISS. That should tell you a thing or two about the complexity and cost of building and launching that stick.
I do have to admit I'm not exactly sure what the advantages are of having the disk further away from the telescope. I suspect it's to do with the interaction between the light and the edge of the disk, but I'm not sure.
https://www.jpl.nasa.gov/news/starshade-would-take-formation...
Edit: Just to be clear on status of this, Starshade is still in early technology demonstration phase that they can actually build the shade and do the formation maintenance. This is not in full build or slated to launch any time soon.
EDIT: maybe not so counterintuitive after all: if you scale everything up, you get a higher fidelity sensor and more signal to noise. Same reason telescopes want to be big: to collect more light especially from dim signals. Distance of the occulter then reduces perspective distortion that would eclipse the inner parts of the sensor more than the outer ones. Just my speculation though.
When needed to achieve the mission, new technology will be developed - sometimes the whole point of a mission is specifically to develop new technology. In this case, one of the major goals of the mission is to develop formation flying technology. Learn what the pitfalls and the tricky bits are, and make the technology available for future missions.
But when the mission can be achieved with old technology - technology with a long record of being used in space, where the problems are known and understood, where we know what works and what causes problems - then the mission will use old technology.
If you use newer technology, there's always a risk that you'll hit a new issue, previously unknown. Maybe you can work around it, maybe you can't. But this isn't web development where you can refactor, switch to a new framework and continuous deploy your way out of it. For the hardware, you get one launch and that's it. Why run the risk if you can avoid it? It'd be a shame if the mission can't achieve its primary objective (learning about formation flying) because it chose some new type of thruster, and encountered some new issue with it.
Started with what you said - a simple gas pressurized and a single valve.
Slowly more and more was added until we get to current rocket designs with multiple stages or active pressurization / fuel transfer and all that entails.
Wish I could find it again.
[0] https://en.wikipedia.org/wiki/Field-emission_electric_propul... [1] https://www.esa.int/Enabling_Support/Space_Engineering_Techn...
The FEEP thrusters I've seen had a hefty power penalty to keep it on standby, and a long warmup time. Cold gas uses more propellant mass per unit impulse, but it can still come out ahead in total size/weight/power.
I don't know the power budget for the satellite, but we can make an educated guess : the occulter is 1.4 meter diameter, or a surface area of 1.54 square meter. That's an upper bound for the surface area of the solar panels - there's nothing sticking out beyond the disk, that would interfere with observations.
Solar power at earth is about 1.3kW/sqm, solar panels are maybe 20% to 30% efficient. That puts you in the ballpark of 400 to 600W.
150W on standby would be a pretty big bite out of your power budget.
https://www.esa.int/Science_Exploration/Space_Science/Captur...
I'm pretty sure the risk of collision has been analysed to death. I would expect they've analysed what would happen if one or both devices suddenly stop listening to commands, and that even then there's essentially no risk.
And flying formation, be it in space or in the air, by definition involves getting as close to zero relative velocity as possible . . . or else you aren't in formation.