NASA - Near Earth Objects Surveyor (NEOS)

[Bob Shaw]

Rubin is primarily a southern hemisphere observatory. A northern hemisphere resource is also required, ground or space based.

[Blackstar]

It appears that Rubin just made Neo obsolete?

No.

[Star One]

Rubin is primarily a southern hemisphere observatory. A northern hemisphere resource is also required, ground or space based.

Has there ever been a proposal for an equivalent ground based resource to Rubin, covering the northern hemisphere?

[LouScheffer]

Appears Rubin just made Neo obsolete?

No.  Rubin is great but it has some limitations.  As a ground based telescope, it can only work when it's dark.  So it can only look out from the sun.  Asteroids that are entirely, or mostly within the Earth's orbit will be missed, as will ones that are in more-or-less Earth's orbit, but trailing or leading the Earth.  NEO as a space telescope does not need to look through the atmosphere, and can look much close to the Sun and see these asteroids.

In particular, the asteroids that NEO can see, but Rubin cannot, are among the ones most dangerous to Earth.  Rubin will find zillions of asteroids, but it's strongly biased towards the non-dangerous ones.

NEO also works in the infrared, which is much better for determining sizes.  This is because visible light telescopes, like Rubin, can't tell a large dark asteroid from a smaller highly reflective one (and both are common).  But in the infrared, as the asteroid needs to be in thermal balance, there is much less variation in brightness as a function of size.  And since impact energy goes as the cube of the radius, finding the size is important.

[LouScheffer]

Rubin is primarily a southern hemisphere observatory. A northern hemisphere resource is also required, ground or space based.

Has there ever been a proposal for an equivalent ground based resource to Rubin, covering the northern hemisphere?

Pan-STARRS is a northern hemisphere sky survey, also with a large field of view and a fast cadence.  One of its main goals is looking for asteroids and other changing objects.  But it uses smaller (1.8 meter ) telescopes and older technology.

For detecting asteroids, though, there is little need for another Rubin in the northern hemisphere.  Almost all asteroids are in or near the plane of the solar system.  Any facility, as long as they are not too far north or south, can see the whole asteroid belt just fine.

[Eric Hedman]

A little more info from the official website on the Rubin 8.4 meter Telescope:

https://rubinobservatory.org/about

While I don't think it is planned to do the same kind of 10 day sky surveys, the next great telescope is under development for the northern hemisphere at roughly 20 degrees north in Hawaii.  It should be able to do a lot of detailed followup work on what the Rubin telescope finds at least for part of the sky. The site for the Thirty Meter Telescope where you can follow its development is:

https://www.tmt.org/

 

[StraumliBlight]

While I don't think it is planned to do the same kind of 10 day sky surveys, the next great telescope is under development for the northern hemisphere at roughly 20 degrees north in Hawaii.  It should be able to do a lot of detailed followup work on what the Rubin telescope finds at least for part of the sky. The site for the Thirty Meter Telescope where you can follow its development is:

FY 2026 NSF Budget Request to Congress [May 30]

Design of Potential New Major Facility Construction Project. Given the unaffordability of continuing funding two different multi-billion dollar telescopes, NSF will advance the Giant Magellan Telescope (GMT) into the Major Facility Final Design Phase, but the Thirty Meter Telescope (TMT) will not advance to the Final Design Phase and will not receive additional commitment of funds from NSF.

NSF has received assurances from the GMT project that it can complete the final design phase without further investments. Moving into the final design phase does not guarantee that a project will be approved for construction, and doing so does not obligate the agency to provide any further funding.

The FY 2026 Request supports continued design of a single telescope within the U.S. Extremely Large Telescope (ELT) program.

[Blackstar]

Appears Rubin just made Neo obsolete?

No.  Rubin is great but it has some limitations.  As a ground based telescope, it can only work when it's dark.  So it can only look out from the sun.  Asteroids that are entirely, or mostly within the Earth's orbit will be missed, as will ones that are in more-or-less Earth's orbit, but trailing or leading the Earth.  NEO as a space telescope does not need to look through the atmosphere, and can look much close to the Sun and see these asteroids.

In particular, the asteroids that NEO can see, but Rubin cannot, are among the ones most dangerous to Earth.  Rubin will find zillions of asteroids, but it's strongly biased towards the non-dangerous ones.

NEO also works in the infrared, which is much better for determining sizes.  This is because visible light telescopes, like Rubin, can't tell a large dark asteroid from a smaller highly reflective one (and both are common).  But in the infrared, as the asteroid needs to be in thermal balance, there is much less variation in brightness as a function of size.  And since impact energy goes as the cube of the radius, finding the size is important.

Yes, all those reasons and a few more. Keep in mind that NEOs are very dark. They are the same albedo as freshly laid asphalt. It is easier to detect them and to measure them in the infrared than visible light, and for that you need a space based telescope.

Back in 2019 I was the study director for the attached study. We knew about Rubin (not called that yet), and many people had modeled what that telescope would detect, so finding a whole bunch of asteroids is not a surprise to the community. That is discussed in our report. You can see that here. Even with two of those telescopes, the NEO detection rate would still be limited.

You can look at this report and read the relevant points. It was one step in getting NEO Surveyor approved. (I cannot go into it here, but the reason NASA requested this study is a doozy of a story.)

[Blackstar]

I should add that Rubin will be very helpful with NEO detection. It's a good addition. And we'll learn new things. But it won't achieve the goal of detecting 90% of NEOs 140 meters in diameter or greater in any reasonable amount of time. To do that, you need a space based IR telescope.

Also, this is new:

https://www.leonarddavid.com/planetary-defense-strategy-new-findings-from-nasa-inspector-general/

[LouScheffer]

[...]
Keep in mind that NEOs are very dark. They are the same albedo as freshly laid asphalt. It is easier to detect them and to measure them in the infrared than visible light, and for that you need a space based telescope.
[...]
Back in 2019 I was the study director for the attached study. We knew about Rubin (not called that yet), and many people had modeled what that telescope would detect, so finding a whole bunch of asteroids is not a surprise to the community. That is discussed in our report. You can see that here. Even with two of those telescopes, the NEO detection rate would still be limited.
[...]

Here is a figure from BlackStar's report, on which I've annotated the bands used by Rubin (320-1060 nm) and NEOS (4-5.2 and 6-10 microns).   This makes it very clear that Rubin is measuring reflected light, and NEOS thermal emission.  It's a big part of the many reasons why the capabilities are different.

[Blackstar]

Here is a figure from BlackStar's report, on which I've annotated the bands used by Rubin (320-1060 nm) and NEOS (4-5.2 and 6-10 microns).   This makes it very clear that Rubin is measuring reflected light, and NEOS thermal emission.  It's a big part of the many reasons why the capabilities are different.

There's another chart in there showing detection rates with Rubin and also with a space based telescope. With Rubin you could eventually reach the desired detection rate, but it takes something like 40+ years of operations (I may be off on that number). Our committee determined that any program that requires something like 20+ years of operations to achieve its goal was not realistic.

I can find the chart, or somebody else can.

[jebbo]

There's another chart in there showing detection rates with Rubin and also with a space based telescope. With Rubin you could eventually reach the desired detection rate, but it takes something like 40+ years of operations (I may be off on that number). Our committee determined that any program that requires something like 20+ years of operations to achieve its goal was not realistic.

I can find the chart, or somebody else can.

Here it is ... Rubin was previously the Large Synoptic Survey Telescope, so obviously, the LSST line.

For fun, the LSST acronym is preserved by Rubin in the name of its main survey product: Legacy Survey of Space and Time

--- Tony

[Star One]

I’ve read reports that if planet nine exists that this will be proven or disproven in the first year of Rubin’s operation. How much truth is there in this statement, or is just so much media nonsense?

[StraumliBlight]

I’ve read reports that if planet nine exists that this will be proven or disproven in the first year of Rubin’s operation. How much truth is there in this statement, or is just so much media nonsense?

NPR: If Planet Nine is out there, this telescope might actually find it

If Planet 9 is real, this observatory has around a 70 to 80 percent chance of finding it, he estimates, adding that it's not a sure thing because there are so many uncertainties.

"We don't know the size of the planet. We don't know the reflectivity of the planet. We don't know the distance of the planet," says Sheppard. "Those three things will determine how bright this planet actually is."

If Planet 9 is on the smaller side, dark, and really far away, he explains, "it's going to be on the edge of Vera Rubin detection, and Vera Rubin may not find it."

[Blackstar]

Here it is ... Rubin was previously the Large Synoptic Survey Telescope, so obviously, the LSST line.

That's it. Somebody on our committee generated that chart. I think we also modeled a second LSST, but it doesn't equal the space-based IR telescope line, and we did not believe that a second LSST was politically feasible. Also, you could bump up the LSST line a bit if you devoted LSST entirely to NEO detection. Right now, NEO detection is (I think) a side effect of the main survey mission, although I think they might have some telescope time dedicated to NEO detection, or at least follow-up.

But going back to my earlier point, the fact that Rubin is detecting a bunch of NEOs is not unexpected. And I doubt that it will detect more than originally expected, because the populations of NEOs can be predicted statistically, with error margins, and it would be really weird if those statistics are grossly wrong.