Subject: existence proof of design reference mission

From: Jeremy Mould

Submitted: Mon, 28 Apr 2003 05:53:37 -0700

Message number: 129 (previous: 128, next: 130 up: Index)

>The next email supplies the postscript plot which accompanies this message.
>Here's a model which can serve as an existence proof of a DRM. And a plot of a 
>limiting magnitude distribution function, where each curve is the number of steradians 
>whose limiting magnitude is shallower than the abscissa.
>
>Strawman DRM
>We assume a visit is 30 seconds and consists of a red and alternate filter observation.
>Each field is visited 5 times per month in clear weather and 5 times per month in cloudy 
>weather. No explicit allowance for moon. 
>In year n, only fields with RA = m hours + n*6 minutes are observed for 0<n<10 and 
>0<m<24.
>Each declination strip gets equal time, starting at (-/+)30 degrees declination and 
>going to (+/-)90 degrees. 
>30 seconds is the total visit time and yields one limiting magnitude 
>image of r = 24 and one of b = 24, where b is one of two alternate filters.
>8 hour nights occur all year long.
>Limiting magnitude is independent of zenith distance or seeing.
>
>Preliminary Conclusions
>A 10 year DRM does exist which would meet the rough scientific 
>requirements, provided alternate filters don't have to exceed 26.5 over 
>large areas of sky.
>If the number of alternate filters were doubled, the blue and green curves would move 
>bodily to the left by 0.375 mag.
>If the single visit limiting blue mag were only 23 in the time the limiting red mag is 24, the blue curve moves to the left by 1 mag.
>
>This existence proof DRM only looks at ~1 sr per year. But that violates no
>current requirement. If it became a requirement to look at 10 sr per year,
>it would be easy to hybridize the all-sky/year and repeat-often strategy
>and still end up with the plot provided here. Zeljko's cadence, in which
>one of the 5 visits per month is same night, would probably not change
>the plot.
> 
>It is also not hard to imagine observing strategies which change the shapes of these curves significantly.


LSST LSST LSST LSST LSST    Mailing List Server   LSST LSST LSST LSST LSST LSST
LSST
LSST  This is message 129 in the lsst-general archive, URL
LSST         http://www.astro.princeton.edu/~dss/LSST/lsst-general/msg.129.html
LSST         http://www.astro.princeton.edu/cgi-bin/LSSTmailinglists.pl/show_subscription?list=lsst-general
LSST  The index is at http://www.astro.princeton.edu/~dss/LSST/lsst-general/INDEX.html
LSST  To join/leave the list, send mail to lsst-request@astro.princeton.edu
LSST  To post a message, mail it to lsst-general@astro.princeton.edu
LSST
LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST