spinflip @spinflip@social.cleverlibre.org

Anyway, that's all background. Today I spent a few hours trying to set up python scripts to find the most recent Sentinel passes over a given geographical location and download the associated imagery products. This would almost certainly be trivial for anyone with a proper computing background, but for this procrastinating chemist the steps involved learning how to:

• Find the relevant API and options: ✔️, not too bad
• Make an authenticated HTTP call to the constructed URI ✔️
• Parse the XML returned into a pandas dataframe containing imaging modes/acquisition time and date/unique ID for each frame containing the specified lat/lon location ✔️
• Download each ~1.8 GB image into a folder for processing. Still in progress: I've found out how to make an authenticated http GET request that *should* be streaming the retrieved file to storage, but the connection seems unstable and I can't get the download to finish. Sorting this out is the next thing I need to do: when I've got a way to download and archive the specified files, it'll be time start looking into automated processing and analysis. Still not even really sure what I'm trying to achieve, but I'm having fun and learning stuff so far!

@mikemcdonald83@mastodon.social I have no real understanding of the history that led to what we have access to today, bur 100% agree. Interferometry is the real mindfuck to me: I get how it works, but the tolerances on orbital parameters + onboard clock timing to get comparable data over multiple passes must be absolutely insane. How many orders of the earth's gravitational field terms do you need to know for it to be possible?

@pkok yeah, there's obviously a huge amount of national and commercial stuff that you can't access (or have to pay for: the best publicly available commercial imagery nowadays is almost certainly better than what the US had access to for most of the Cold War). That said, the free offerings are really cool. Landsat is low-res optical imagery that's been running forever (you could independently go measure the last 30 years of land clearing in the Amazon), and the Sentinel program covers a huge range of data: optical, radar, IR bands for temperature measurement, spectroscopy for atmospheric gas quantification… the data are all available online from the ESA for anyone interested to go wild with

SAR imagery does not have amazing spatial resolution, but is often good enough to do things like identify shipping. Water is a uniquely flat surface, so metal objects floating on water give a good return against a low background signal*. Some computationally demanding image processing later, and you can pick out ship locations. I've got a vague idea that it could be interesting to find ships in the territorial waters of North Korea, correlate against AIS tracks, and try to find some sanction-busting shipping running dark without AIS.

*This makes me wonder: the USSR really struggled with power requirements for the radar on its RORSAT ocean-monitoring satellites, to the point that it ended up having to power them using the only nuclear reactors to be launched into space. Why is SAR so much more efficient?

I've got a hobby-interest in remote sensing (satellite imagery). Over the past couple of days, I've been playing around with data from the ESA's Sentinel-1 mission. The ESA (being cool and European Union-y) makes most of the data from Sentinel series of satellites freely accessible to the public, and provides some decent software for processing and analysing the data.

Sentinel-1 is a synthetic aperture radar (SAR) satellite. I don't fully understand the physics behind SAR, but it's basically an active radar measurement of the ground track the satellite passes over. Different surfaces give different sorts of radar returns (measured as a change in polarisation), and so SAR can be used to classify different terrains (crops, forests, grasslands, rock, etc), like in the false-colour image of Flevoland I've attached. Resolution is moderate: for Sentinel-1, each pixel ends up being about 4x4 m on the ground.

@black_sun I feel that might well depend a lot on your student-supervisor relationship! Mine has been happy to let me pursue whatever seemed most interesting at the time, which has almost entirely been my own projects. With hindsight I really could have done with more direction, but I've certainly had an interesting time

@freemo @arteteco well, the website is pretty clear about the STEM focus (which honestly isn't always the most promising sign for critical thinking). Still, we'll see how it goes. Hopefully we'll be able to find things to talk about other than Mastodon itself

@arteteco Thank you! I'm not 100% sold on subject-focused instances making sense in the long term (am I more a researcher, or a film fan? or should I self-sort based on my politics?), but maybe it'll help get M off the ground

@kara@witchcraft.cafe That sucks. I'm close to the end of a PhD now: no idea if I'll committing to carry on with research, but I've had a pretty good time doing it so far. That said, the horror stories I've heard of life-sucking American grad research culture make me really fucking glad to have done my work in Australia, where you're allowed to go home in the evening and stay home at the weekend.

@kara@witchcraft.cafe ah, nice! All those nanostructure/surface things kind of scare me, tbh. Much easier when your objects are well-defined molecules, MWs are a few thousand or less, and you can solve any conceivable problem with NMR + MS.

@GIMcGrew Another one here! Who have you found?

@qwert@mastodon.technology I wasn't there for forums in the 90s, but I was on lots in the early 2000s and I think they were pretty similar. The major thing was the stability of the userbases: it was *hard* to find communities of any sort of like-minded individuals during that era of the internet, so any that you did find became very valuable. A good forum in 2005 could well have a significant chunk of the members it had had in 1995, as well as newer people making an effort to integrate with the already-existing community.

@kara@witchcraft.cafe I've never done glass etching, so please take everything I say with a pinch of (harmless NaCl) salt

@kara@witchcraft.cafe no, but I'd imagine it isn't. Still, how stable is SiF6 to hydrolysis? I don't know, but I'd guess it exists in equilibrium with silicon oxides + free HF

@kara@witchcraft.cafe soluble fluorides are also usually pretty bad news. That kind of comes with the territory, of course, but I wouldn't really want to leave any more hanging around than is necessary.

@black_sun hah, thanks. That thesis deadline is starting to get awfully close…
I honestly have no idea if I'll be looking for research work after my PhD or not, but so far I'm glad I decided to do it. Being given the time and support to spend a few years working on cool projects with minimal oversight is pretty great :)

@freemo hah, don't set your expectations too high but we'll see. Currently doing lots of analytical work and not as much synthesis, but feel free to ask any questions you might have and I'll do my best

#introduction to the above: forgot it the first time because I've been at work for too long