Author Topic: OSTP Response to Congress on Near-Earth Objects  (Read 6232 times)


Offline simonbp

Re: OSTP Response to Congress on Near-Earth Objects
« Reply #1 on: 10/24/2010 08:53 AM »
One significant point for Human Spaceflight from these letters is the estimation that ~85-90% of the NEAs greater than 1.4 km have been found. So, even if the cut-off for human flights is 500 meters or so, the vast majority of the potential targets are already known...

Offline HappyMartian

  • Senior Member
  • *****
  • Posts: 2715
  • Tap the Moon's water!
  • Asia
  • Liked: 14
  • Likes Given: 2
Re: OSTP Response to Congress on Near-Earth Objects
« Reply #2 on: 10/24/2010 12:34 PM »
See a previous thread at:

...with online streaming live for those who cannot attend...

MEDIA ADVISORY: M10-105

NASA HOSTS WORKSHOP TO DISCUSS EXPLORING NEAR EARTH OBJECTS
......

The primary goals for the workshop are to increase the collective understanding of NEOs, communicate NASA's preliminary plans for a human mission to a NEO, and get input on proposed mission objectives.
The workshop includes a series of briefings, panels, and breakout sessions.
....


See also: Possible threat to Earth by asteroids among issues at UN debate on outer space
At:  http://www.spaceref.com/news/viewpr.html?pid=31916

Cheers!

Edited to add SpaceRef note.
« Last Edit: 10/24/2010 02:27 PM by HappyMartian »
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

Offline spacester

  • Member
  • Full Member
  • **
  • Posts: 221
  • Liked: 1
  • Likes Given: 3
Re: OSTP Response to Congress on Near-Earth Objects
« Reply #3 on: 10/24/2010 08:20 PM »
One significant point for Human Spaceflight from these letters is the estimation that ~85-90% of the NEAs greater than 1.4 km have been found. So, even if the cut-off for human flights is 500 meters or so, the vast majority of the potential targets are already known...

Except for the ones with orbits entirely within Earth's orbit, which we will never see from Earth's surface. A tentative name for them was "Arjunas", a fourth class to be added to Apollos, Atens and Amors. I saw a new name for them the other day and forgot it already.

My understanding is that we have virtually no idea how many or how big they are.

Offline simonbp

Re: OSTP Response to Congress on Near-Earth Objects
« Reply #4 on: 10/25/2010 03:25 AM »
Except for the ones with orbits entirely within Earth's orbit, which we will never see from Earth's surface. A tentative name for them was "Arjunas", a fourth class to be added to Apollos, Atens and Amors. I saw a new name for them the other day and forgot it already.

My understanding is that we have virtually no idea how many or how big they are.

Not quite not idea; we can do orbital simulations to see how stable they would be, and the answer is not very. Also, there have been some surveys (hard from Earth, but not impossible), and there aren't much results, which jives with the simulations.

From a HSF perspective, such objects are the hardest possible NEOs to reach, and the worst from a radiation perspective. So, not exactly great (or numerous) targets...

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 10576
  • Liked: 2157
  • Likes Given: 1
Re: OSTP Response to Congress on Near-Earth Objects
« Reply #5 on: 10/25/2010 03:59 AM »
So, even if the cut-off for human flights is 500 meters or so, the vast majority of the potential targets are already known...

Why do you think the cut-off is 500 meters?

(You're off by an order of magnitude.)

Okay, that sounds too snarky, but I don't want to be snarky.  From what I understand, they are looking down to 50 meters, because that is considered the size that could do considerable damage if it hit Earth.  So they've tied it to the impact threat, which in some ways makes sense and in other ways doesn't (you would like the data, but you would not send humans to deflect an asteroid).  Considering that there are a lot of rocks below, say, 500 meters that have not been detected (in fact, virtually all of them), this should provide a lot of opportunities.

But it also opens up other issues.  Assume that the goal really is to do this by 2025.  It would take at least seven or more years before you can start to really do the kind of extensive surveying that is necessary to find good targets (roughly that amount of time to build a spacecraft or telescope).  And it will take several years to actually survey.  That means that you don't start collecting good targets until very late in this decade.
« Last Edit: 10/25/2010 04:03 PM by Blackstar »

Offline spacester

  • Member
  • Full Member
  • **
  • Posts: 221
  • Liked: 1
  • Likes Given: 3
Re: OSTP Response to Congress on Near-Earth Objects
« Reply #6 on: 10/29/2010 02:57 AM »
Except for the ones with orbits entirely within Earth's orbit, which we will never see from Earth's surface. A tentative name for them was "Arjunas", a fourth class to be added to Apollos, Atens and Amors. I saw a new name for them the other day and forgot it already.

My understanding is that we have virtually no idea how many or how big they are.

Not quite not idea; we can do orbital simulations to see how stable they would be, and the answer is not very. Also, there have been some surveys (hard from Earth, but not impossible), and there aren't much results, which jives with the simulations.

From a HSF perspective, such objects are the hardest possible NEOs to reach, and the worst from a radiation perspective. So, not exactly great (or numerous) targets...

Ah, that's good to know. I do remain a bit unconvinced they are not plentiful. I know their orbits can be chaotic but my sheer curiosity makes me want to know about them.

Planetary scientists are often surprised, but yeah, they've gotten really good at those orbital simulations so I probably shouldn't doubt that answer. I can't help myself, I've always been curious about them, I guess simply because they never appear in our night-time sky.

Good point on HSF targets but I'm a John H Lewis fan, so it's just that much more solar energy for the smelters ;D

I also would love to have some actual targets to see how accessible they are for repeated visits. Not easy I know, but we do have Venus to work with.

Tags: