Subject: Potential Observing Tests for LSST
From: Andrew Connolly
Submitted: Fri, 25 Apr 2003 15:16:41 -0400
Message number: 125
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Attached below is a list of test observations that came out of the data
management meeting on photometry and astrometry with LSST (data we can
take today to address a number of outstanding questions). These are
being put together into a directors/engineering time proposal (for NOAO
facilities) over the next day or so. If there are additional tests that
would be useful or other resources that we can get access to (ie other
types of devices that may be competitive) please suggest them.
cheers
Andy
Program 1: Chromatic Differential Refraction and its impact on image
subtraction
Goal: To measure the effect of chromatic differential refraction on
image subtraction and coaddition by following a single imaging field
over a wide range of zenith distances and observing conditions. This
requires periodic monitoring of a single field and should be undertaken
for more than one telescope system targetting identical fields (with
~0.25 arcsec pixels).
Telescope/instrument required for test:
CTIO 4m Mosaic
WIYN Mini-mosaic
Observing procedure: Observe one of the equatorial fields from the "w
project" team data between the RA range 00-01 hrs. A field should be
followed and observed every hour in each band during one photometric
night with good seeing and then intermittently throughout the semester
at a range of hour angles and observing conditions (i.e. cirrus, seeing,
moon). All observations should be undertaken in B, R and I passbands (R
and I are part of Supernova team data which will be used for calibration
of photometry) with the ADC switched off. Integration times should be
~120s, which go to m~24 (at S/N of ~5) in V and R, roughly corresponding
to the depth of individual exposures with the LSST.
Calibration data required are a set of bias frames and dome and sky
flats in the B, R, I bands
Available Fields (any from Supernova team): RA range 00-01 hrs +00
degrees Field list and finders can be found at
http://www.ctio.noao.edu/wproject/fields
NOTE: *All* of this data will be made public through the NSA (ie NOAO
not the government) with no proprietary period.
TIME REQUEST: - Approx. half of one *photometric* night with good seeing
on Blanco and WIYN.
-----
Program 2: Scale and integration dependence of astrometric uncertainties
Goal: To test the astrometric quality (rms between pairwise distances
for a set of stars observed over a series of exposures) as a function of
angular scale and integration time. This is to be done for a range of
telescopes, CCDs and cameras (i.e. what relatively modern cameras can
achieve).
Telescope/Equipment used in test:
WIYN mini-mosaic
Mayall 4m MOSAIC
CTIO 4m MOSAIC + MASS (to study where in atm the effect is coming from)
CFHT Megacam (data is already in hand and OTA data should be available?)
Deep Depletion Devices
Observing procedure: Observe open clusters (preferably with existing
astrometric solutions). Take 5 exposures for each integration time of
1s, 10s, 30s and 60s in the R band. All observations should be done with
and ADC switched off. This series should be obtained as close to zenith
as possible and for a zenith distance of approximately 60 degrees.
Calibration data required is a set of bias frames and dome flats in the
R band.
Available clusters through this and the next semester
M11: 19hrs -6 degrees
M67: 9hrs +11 degrees
Omega-Cen: 13hrs -47 degrees
OUTSTANDING QUESTION: Do you want to dither between frames (I assume
not)
OUTSTANDING QUESTION: Can we get access to a deep depletion device and
repeat this for B and R band photometry.
TIME REQUEST: - Approx. two hours of telescope time on each telescope.
-----
Program 3: Photometry with saturated stars
Goal: To test whether 1% photometry is feasible with saturated stars
(assuming the saturation is not in the analog-to-digital conversion).
Telescope/instrument required for test:
CTIO 4m Mosaic
88inch OTA CCDs
Deep Depletion Device (e.g. MARS)
Gemini EEV cameras
CFHT Megacam
Observing procedure: Observe a Landolt standard field with isolated
stars over a range of integration times; 4s, 8s, 16s, 32s, 64s, 128s,
256s (note stars below should saturate in 40s). Each exposure sequence
should be repeated 5 times. All observations are in the R band and with
the ADC corrector switched off. Observations should be done at low
airmass
Calibration data required are a set of bias frames and dome flats in the
R band
OUTSTANDING QUESTION: Do we know this is not color dependent? One could
imagine that it might be, due to the different areas of the CCD with
which the photons interact. How about doing it both in I and in B (no
R) to maximize the color difference?
Available Fields (any non-crowded Landolt Field)
G163 27 10:57:35 -07:31:23 (14.338)
L92-249 00:54:34 +00:41:05 (V=14.325)
TIME REQUEST:
- Approx. two hours of telescope time on each telescope.
-----
Program 4: Test of CTE effects on Astrometry and Photometry
Goals: To test the effect of CTE on astrometry and photometry by
observing a single field through twilight as the sky background
increases. This only needs to be done on for a single
telescope/instrument
Telescope/instrument required for test:
CTIO 4m Mosaic
OTA CCDs
Deep depletion device
Observing procedure: Observe one Landolt field repeatedly through
twilight until the background is 1/2 the full well of the
device. Observations should be undertaken in the R band without the ADC
running. Observations must be undertaken in photometric conditions. For
target fields below a series of 10s exposures would suffice.
Calibration data required are a set of bias frames and dome flats in the
R band.
Available Fields (any field):
G163 27 10:57:35 -07:31:23 (14.338)
L92-249 00:54:34 +00:41:05 (V=14.325)
TIME REQUEST: - Approx. 20-30 min of telescope time during twilight
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