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Vera C. Rubin Observatory first images

rubinobservatory.org

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Re: Vera C. Rubin Observatory first images

#161

Post by cogman10 »

mapt wrote: post #159
cogman10 wrote: post #145

Earlier quoted context omitted.

I think where the calculations are breaking down is in the probability of asteroid strikes. All the math assumes that the probabilities will follow historic trends and is relatively static. With single digit events, we really have no way in knowing what the actual likelihood of impact is. It could be 1 in 100 million, it could actually be 1 in 1 million and we've been rolling a bunch of nat 20s. Before we build out t…

While I'm strongly supportive of survey astronomy in general... We can already say that we have very high completion of cataloguing near-Earth objects that are anywhere near extinction-event / Chicxulub-sized (~10km), and have a majority of catastrophic / country-killer (~1km), and are digging deeper and deeper into regional / city-killer (~100m) bodies. What we don't have is comets. Comets on long period orbits just…

Will rubin detect comets? I'd assume not as it seems like they'll only really be visible as they approach the sun (or if they end up blocking a line of stars).

Re: Vera C. Rubin Observatory first images

#162

Post by mapt »

cogman10 wrote: post #161
mapt wrote: post #159

Earlier quoted context omitted.

While I'm strongly supportive of survey astronomy in general... We can already say that we have very high completion of cataloguing near-Earth objects that are anywhere near extinction-event / Chicxulub-sized (~10km), and have a majority of catastrophic / country-killer (~1km), and are digging deeper and deeper into regional / city-killer (~100m) bodies. What we don't have is comets. Comets on long period orbits just…

Will rubin detect comets? I'd assume not as it seems like they'll only really be visible as they approach the sun (or if they end up blocking a line of stars).

The problem is that the difference in optical/NIR brightness (apparent magnitude) between a long-period comet core that's going to hit us in 1000 years, and a long-period comet core that's going to hit us in six months, might be a factor 10^12 (magnitude 10 vs magnitude 40) or worse. Normally brightness drops off with distance squared for light sources, but comets without any tail or halo aren't emitting all that much light, they're reflecting it, and (except for a very brief period) they're about as far from us as they are from the sun. This means that brightness drops with distance to the fourth power. Cometary tails also only offgas a significant amount near the sun. Comet cores are expected to be extremely dark / low-reflectivity due to space weathering producing a carbon coating not unlike chimney-creosote.

You can fight this a bit by working in the thermal infrared, which you really need a specific sort of space telescope for. But long-period comets and hyperbolic impactors will be a probabilistic threat for the foreseeable future. I would say "Be thankful that they're so rare", but the data from observatories like Rubin on these bodies during points of their orbit where they're close enough to the sun to actually detect, is necessary to statistically characterize their existence with any confidence.

Re: Vera C. Rubin Observatory first images

#163

Post by dekhn »

spacecadet wrote: post #103
Tepix wrote: post #95

Earlier quoted context omitted.

If you’re dealing with a fairly constant amount of data every day for years, using the cloud will be way more expensive than necessary.

The whole thread comes off as an AWS sales pitch...

I've setup and built my own machines and clusters, as well as setting up grids, and industrial scale infrastructure. I've seen many closet clusters, and clusters administrated by grad students. Since then, I've gone nearly 100% cloud (with a strong preference for AWS).

In my experience, there are many tradeoffs using cloud but I think when you consider the entire context (people-cost-time-productivity) AWS ends up being a very powerful way to implement scientific infrastructure. However, in consortia like this, it's usually architected in a way that people with local infrastructure (campus clusters, colo) can contribute- although they tend to be "leaf" nodes in processing pipelines, rather than central players.

Re: Vera C. Rubin Observatory first images

#164

Post by dekhn »

gregw2 wrote: post #115
dekhn wrote: post #68

Earlier quoted context omitted.

I've worked on quite a few large-scale scientific collaborations like this (and also worked on/talked to the lead scientists of LSST) and typically, the end groups that do science aren't the ones handling the massive infrastructure. That typically goes to well-funded sites with great infrastructure who then provide straightforward ways for the smaller science groups to operate on the bits of data they care about. Her…

Why move the data? Why not just enable permissions on cloud sharing a la Snowflake or iceberg?

Sure, that also works, although it often leads to problems around cost and scalability and environment customization.

Re: Vera C. Rubin Observatory first images

#166

Post by ianburrell »

myrmidon wrote: post #158
adgjlsfhk1 wrote: post #148

Earlier quoted context omitted.

one thing this analysis is missing is the smaller asteroids. for every planet altering asteroid, there are hundreds that could cause a tsunami that would wipe out a few cities

Good point, but I think those are "worth" less from a risk-analysis PoV: 1km diameter is apparently about 200 times more likely (1/500000 years) according to wiki, but would need to kill 40M people to match the extinction-level asteroid risk (so basically-- unmitigated hit on Tokyo or bust). To be honest, I think the 1km diameter range might still be a major fraction of the actual risk, because the estimates around "…

There is also a difference between mass extinction asteroid like dinosaurs, and one that destroys human civilization. Smaller one wouldn't extinct humanity but would kill most of the people alive. 1km might be big enough to do that depending on the amount of dust and cooling.

Re: Vera C. Rubin Observatory first images

#167

Post by ianburrell »

kkylin wrote: post #48
robotnikman wrote: post #46

Earlier quoted context omitted.

>The prompt products are alerts, issued within 60 seconds of observation, about objects that have changed brightness or position relative to archived images of that sky position. Transferring, processing, and differencing such large images within 60 seconds (previous methods took hours, on smaller images) is a significant software engineering problem by itself.[64] >This stage of processing will be performed at a cla…

"Let's look for spy satellites / orbiters" was an "application" I wondered about. My second thought about this was: maybe the US (and possibly other countries) already have something like this, but classified?

There is the Space Surveillance Telescope [1] in Australia. It is similar military telescope for space tracking. It is only 3.5m compared to LSST 8m.

1: https://en.wikipedia.org/wiki/Space_Surveillance_Telescope

Re: Vera C. Rubin Observatory first images

#168

Post by adgjlsfhk1 »

myrmidon wrote: post #158
adgjlsfhk1 wrote: post #148

Earlier quoted context omitted.

one thing this analysis is missing is the smaller asteroids. for every planet altering asteroid, there are hundreds that could cause a tsunami that would wipe out a few cities

Good point, but I think those are "worth" less from a risk-analysis PoV: 1km diameter is apparently about 200 times more likely (1/500000 years) according to wiki, but would need to kill 40M people to match the extinction-level asteroid risk (so basically-- unmitigated hit on Tokyo or bust). To be honest, I think the 1km diameter range might still be a major fraction of the actual risk, because the estimates around "…

they may be worth less, but each class of them bumps up the value of detection since detection helps against all of them.

Re: Vera C. Rubin Observatory first images

#169

Post by jpizagno »

dekhn wrote: post #139
jpizagno wrote: post #119

Earlier quoted context omitted.

You worked on the design? That is interesting. I worked on the simulating the LSST , back in 2008 to 2010. The goal of which was to test the data reduction software. We were on the Image Simulation team. It is surreal to see LSST/Rubin finally get first light. Even more interesting to see who is still working on LSST, and who is not.

We also simulated the LSST- in this case, using Exacycle at google (an idle cycle harvester). We took a star catalog and passed it through a highly accurate ray tracer that simulated the light falling on the sensors (through space, atmosphere, etc). Apparently it found some bug in the design that was fixed before some expensive part was built (my coworkers were the subject matter expert, I mainly built the exacycle s…

Wow! We also had some ray tracing software, and at one point, my job was to deliver the star (and galaxy) catalogs to the Google office in Seattle. If you worked with the Image Simulation team at U. of Washington in Seattle, then our paths almost crossed, and we might've been on conference calls together.

Re: Vera C. Rubin Observatory first images

#170

Post by dekhn »

jpizagno wrote: post #169
dekhn wrote: post #139

Earlier quoted context omitted.

We also simulated the LSST- in this case, using Exacycle at google (an idle cycle harvester). We took a star catalog and passed it through a highly accurate ray tracer that simulated the light falling on the sensors (through space, atmosphere, etc). Apparently it found some bug in the design that was fixed before some expensive part was built (my coworkers were the subject matter expert, I mainly built the exacycle s…

Wow! We also had some ray tracing software, and at one point, my job was to deliver the star (and galaxy) catalogs to the Google office in Seattle. If you worked with the Image Simulation team at U. of Washington in Seattle, then our paths almost crossed, and we might've been on conference calls together.

Yes, you probably interacted with my coworker Jeff (first on this list: https://research.google/blog/millions-of-core-hours-awarded-...)
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