Co-observing with Rubin

rseaman · January 24, 2025, 3:09am

Howdy, old and new community members have been nudged to use this forum. So here’s a post whose relevance is looming.

Innumerable discussions have centered on follow-up using brokers. Entire paradigms (e.g., VOEvent) and partners (the U.S. VAO) have come and gone. Little has been (publicly) discussed about coordination between other surveys, though, of course, many must have been thinking about such details. One example is coordination of Rubin moving object detections with the Planetary Defense community. Candidate NEOs will be fed into the usual NEO confirmation page, Scout and Sentry Virtual Impactors, NEOfixer targeting broker, etc. But no specific planning has gone into coordination of survey footprints between the ongoing northern NEO surveys and Rubin, or between near future southern NEO-optimized surveys and Rubin. And simulations with the NEO Surveyor mission (east and west footprints) and Rubin.

Thoughts about optimizing surveys strategies? Rubin’s sensitivity to moving objects will be quite different from the NEO-optimized surveys, and it may simply be that we allow the overlap to happen and the more nimble surveys (same-night candidates, that is) will continue to score discoveries that Rubin will have a nice cottage industry following up.

What are the appropriate figures of merit? Orbital arc length? Maximizing the number of NEOs with both optical and infrared observations? 140-m NEOs? PHAs? 50-m PHAs?

What infrastructure will be needed? A few hour lookahead of Rubin targets? An annual rolling cadence assessment of the North-Ecliptic Spur? Special dispensation for announcing NEO candidates from streaked objects or resulting from the Twilight Survey? What does Rubin need to know about the other NEO surveys? Presumably Jehovah herself wouldn’t be able to modify the main (“universal”) survey, but will tweaks be possible to twilight targets? What questions should I have asked?

ljones · January 24, 2025, 5:24am

Interesting questions.
As you mention -there are many aspects of the survey strategy which are unlikely to be changed without significant thought and effort. I’m not entirely sure what you’re proposing modifying about the survey strategy to coordinate with other surveys, but certainly tracking usefulness of Rubin observations is one of our goals, so the metrics you suggest are reasonable to look at adding to the metrics we already calculate for Rubin alone. (Perhaps in a next-generation version of these metrics which consider real objects observed, rather than model populations). I would note that the SSSC have already indicated their first priority is overall SSO population discovery throughout the solar system with Rubin, which would mean that these would be ranked as secondary metrics at least at first.

Some of the other aspects you mention regarding tools:

few hour lookahead of Rubin targets – this isn’t built out completely yet, but there is infrastructure in the works for publishing the 24-hour ahead-of-time predicted schedule (which will of course be quite inaccurate at that range), a 2-hour ahead-of-time predicted schedule (which becomes more accurate, although not guaranteed), and “next visit” predicted schedule (which really should be very accurate). This will be published via an ObsLocTap service.
I’m not sure what you mean about an annual rolling cadence assessment of the NES … we will make quarterly and annual reports on survey progress, including expected performance at end of survey. The NES doesn’t actually get included in rolling - I should make that more clear on Vera C. Rubin Observatory Survey Strategy — Observing Strategy, only the WFD-level areas are part of the rolling cadence. Could you expand a bit on this?
I don’t know if I have a good comment about announcing NEO candidates from streaked or twilight survey … I probably need to go back and look into the workflow of the SSP and what is included in alerts (I thought streaks would be) or when objects are released as identified (I’m less clear on twilight survey objects which could have four detections but only one night … I imagine they are immediately announced though, to be most useful). @mjuric?
I imagine that if we find the near-sun twilight microsurvey is not being effective in increasing the population of the asteroids it’s intended to boost, that we would modify the microsurvey. I suspect it’s too soon to know what that modification would look like, but it does tie into a topic that’s been on my mind for a while — how do we “close the loop” on our survey strategy metrics, to see if predictions match reality (or in this case, if Rubin is not adding to the overall scientific landscape in a given area, how do we ensure that we’re looking at the right question regarding science impact).

Significant survey strategy changes will have to go through the SCOC, to ensure we’re looking at all sides of a change. But the SCOC do remain a standing committee through operations, and updates to the survey strategy resulting from changes in scientific priorities are certainly something we want to be able to do.

rseaman · January 24, 2025, 1:24pm

This is the community forum and I wasn’t specifically arguing to modify the LSST cadence. Rather, how will the community, including external surveys, make best use of this new resource? That said, as operations approaches, interest will grow about both details and the general behavior of the final survey strategy. For example, what will be the highest effective airmass both for the main survey and twilight? How will nightly, weekly, monthly coverage vary across the MW, NES, and the south pole? No doubt I misused the word “rolling” regarding the NES. Last I heard, coverage of NES was going to be less, and less frequent, than the main survey. Other surveys will be interested in when Rubin will be targeting versus ignoring such regions of the sky.

Rubin is definitely entering a time of loop closing. Some of those loops will be evaluated in context with external projects and surveys. Survey strategy overlaps operational details like telescope maintenance, public outreach, interactions with the science collaborations, etc, not just the cadence formerly known as “synoptic”. One imagines that every day, week, or month during the survey there will be high priority transients or moving objects that will require engagement with external surveys or follow-up.

Over the longer term, for some science cases, coordination with other surveys like NEO Surveyor may flow both ways, certainly at the level of joint publications and forums like this one, perhaps at the level of standing up new web services or SQL queries, building new tools (whether through the offices of a science collaboration or the core Rubin developers), and likely even proposing new third party telescopes or instrumentation down the road. SCOC will be writing letters of support and the more flexible parts of Rubin operations (perhaps including the twilight survey) may evolve.

The subject of this thread is co-observing. Follow-up is naturally adaptive, but external survey science cases may benefit from contemporaneous overlap with Rubin fields, or leading or trailing by hours or days, perhaps with complementary filters or spectra, etc. None of these are new topics, but few of them have been settled down to the level of APIs and service level agreements.