Subject: Re: Strawman science programs for the LSST; please respond!

From: Gary Bernstein

Submitted: 13 Feb 2003 18:23:33 -0500

Message number: 69 (previous: 68, next: 70 up: Index)

Let me suggest a perturbation to Michael's KBO scenario:

>   The LSST has the potential to map out the full dynamical
> distribution of these objects.  This requires a survey that is not
> necessarily confined to the ecliptic plane, going as deep as
> possible.
> 
>   Two-color (g and i?) imaging photometry to 24th mag, two times
> separated by 15-30 minutes, once or twice per lunation, over 15,000
> square degrees. 
> 

This bright-object scenario is fine.  My only comment is that sampling
10-20 times per year is overkill for orbits.  It is important that the
objects be followed for ~3 consecutive years.  But obtaining ~30
observations will enable variability studies, and will likely occur as a
byproduct of other observations.

>   To observe fainter KBO's, to 26th magnitude: 
>     Define a region centered on the Solar System's invariant plane 3
> degrees wide.  Image this twice in a single band for 20 minutes (a
> Plutino will move 1 arcsec in that time), separated by one hour.  Do
> this once per lunation.  
>   (I've limited this to the ecliptic plane, in a single band, to keep
> it finite).    

The following perturbation will reach deeper with less computational
burden, and suggests another scheme for partial coverage of the sky that
might sample the orbital distribution better:

Each observation is 1 contiguous hour, at >45 degrees from opposition to
reduce apparent motion during this hour to ~1".  Repeat one additional
time within 2 months, and twice per year for 2 or more additional years.

The target areas should be strips 3 degrees wide, extending +-20 degrees
from the ecliptic.  Covering this entire area 6 times with the 7 deg^2
LSST FOV then takes 1.2e4 hours of observing, or 4.2 years' worth of
8-hour nights. But 100% coverage is not required; one could for example
consider spacing the 3-degree strips every 12 degrees (1 in 4 coverage)
or some other modulation to optimally sample the expected sky
distribution.  (The sky-plane distribution of KBOs is not expected to
have structures smaller than ~10 degrees in longitude.)
Then we are talking about a years' worth of time, which can be spread
over N survey years.  

Gary



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