Chapter Editors: can you please issue each of your science section writing teams with the following task? Thanks!
Task:
@ivezic would like to know how each science case constrains the observing cadence in several specific ways, and has provided a list of ten questions he would like answered for each science case - his list is below. Not all the questions will be relevant to every science case, but every science case must present its conclusions, and this list of questions is a very good framework to base them on! Some of the questions address relatively simple fine tuning of survey parameters,
while others offer the possibility of dramatic changes. It is particularly valuable to identify
constraints or tradeoffs that hold across a broad swath of science programs, and to understand
which options, if any, are neutral to the science - by having every science case answer these questions, we will be better able to do that.
To illustrate the expected detail level of answers, we also provide an example for each
question (which attempted to reflect real constraints, but are not binding in any way).
1) Can you place constraints on the tradeoff between the sky coverage and coadded depth?
For example, should we maximize the sky coverage (to ~30,000 sq. deg., as e.g. Pan-STARRS)
or the number of detected galaxies (the current baseline with 18,000 sq. deg.)?
Example: Weak lensing science scales with the number of well-measured galaxies. The main
survey area should be optimized to maximize the size of galaxy sample.
2) Can you place constraints on the trade between uniformity of sampling and frequency of
sampling? For example, a rolling cadence can provide enhanced sample rates over part or all
of the survey part of the time, at the cost of reduced sample rate the rest of the time (while
maintaining the nominal total visit counts).
Example: For Type Ia SNe science, light-curve sampling should be about twice as frequent as
for the current baseline cadence. The benefits of this improved sampling would outweigh
the loss of active sky area.
3) Can you place constraints on the tradeoff between the single-visit depth and the number
of visits? Especially in the u band, where longer exposures would minimize the impact of the
readout noise.
Example: The single-visit depth required for detecting RR Lyrae stars to the presumed tidal radius
of the Milky Way is at least r24.5. The single-visit depth required for detecting SNe to redshifts
of about 1, that can be probed with LSST filter complement, is at least r24.5. The increased
number of visits that could be obtained with shallower data would not benefit either science
case.
4) Can you place constraints on the Galactic plane coverage (spatial coverage, temporal
sampling, visits per band)?
Example: Our science program cannot place any constraints on the Galactic plane coverage.
5) Can you place constraints on the fractions of observing time allocated to each band?
Example: Photometric redshift estimates for galaxies require that each band receives at least
10% of the total observing time.
6) Can you place constraints on the cadence for deep drilling fields?
Example: In order to obtain good light-curve templates for SNe, at least one deep drilling field
has to be observed each night in all 6 bands for at least 4 months.
7) Assuming two visits per night, should they be obtained in the same band or not?
Example: The completeness considerations for asteroids suggest that two visits in a given
night should be obtained with the same band.
8) Would your science benefit from a special cadence prescription during commissioning or
early in the survey, such as: acquiring a full 10-yr count of visits for a small area (either in all or in selected bands); a greatly enhanced cadence for a small area?
Example: The deep drilling fields with multi-wavelength data would enable early science results
if LSST data were obtained early.
9) Do you have constraints for sampling of observing conditions (e.g. seeing, dark sky,
airmass), possibly as a function of band, etc.?
Example: Weak lensing science would greatly benefit if the r and i band data were obtained during the best seeing nights.
10) Do you have science drivers that would require real-time exposure time optimization
to obtain nearly constant single-visit limiting depth?
Example: Science programs requiring a minimum single-visit depth (such as Near-Earth Object
survey) would benefit from its uniform distribution.
Finally, if your science would benefit from a cadence methodology not covered by these questions,
please enter a description of this methodology at http://ls.st/yqq
Chapter Editors: can you please issue each of your science section writing teams with the following task? Thanks!
Task:
@ivezic would like to know how each science case constrains the observing cadence in several specific ways, and has provided a list of ten questions he would like answered for each science case - his list is below. Not all the questions will be relevant to every science case, but every science case must present its conclusions, and this list of questions is a very good framework to base them on! Some of the questions address relatively simple fine tuning of survey parameters,
while others offer the possibility of dramatic changes. It is particularly valuable to identify
constraints or tradeoffs that hold across a broad swath of science programs, and to understand
which options, if any, are neutral to the science - by having every science case answer these questions, we will be better able to do that.
To illustrate the expected detail level of answers, we also provide an example for each
question (which attempted to reflect real constraints, but are not binding in any way).
1) Can you place constraints on the tradeoff between the sky coverage and coadded depth?
For example, should we maximize the sky coverage (to ~30,000 sq. deg., as e.g. Pan-STARRS)
or the number of detected galaxies (the current baseline with 18,000 sq. deg.)?
Example: Weak lensing science scales with the number of well-measured galaxies. The main
survey area should be optimized to maximize the size of galaxy sample.
2) Can you place constraints on the trade between uniformity of sampling and frequency of
sampling? For example, a rolling cadence can provide enhanced sample rates over part or all
of the survey part of the time, at the cost of reduced sample rate the rest of the time (while
maintaining the nominal total visit counts).
Example: For Type Ia SNe science, light-curve sampling should be about twice as frequent as
for the current baseline cadence. The benefits of this improved sampling would outweigh
the loss of active sky area.
3) Can you place constraints on the tradeoff between the single-visit depth and the number
of visits? Especially in the u band, where longer exposures would minimize the impact of the
readout noise.
Example: The single-visit depth required for detecting RR Lyrae stars to the presumed tidal radius
of the Milky Way is at least r
24.5. The single-visit depth required for detecting SNe to redshifts24.5. The increasedof about 1, that can be probed with LSST filter complement, is at least r
number of visits that could be obtained with shallower data would not benefit either science
case.
4) Can you place constraints on the Galactic plane coverage (spatial coverage, temporal
sampling, visits per band)?
Example: Our science program cannot place any constraints on the Galactic plane coverage.
5) Can you place constraints on the fractions of observing time allocated to each band?
Example: Photometric redshift estimates for galaxies require that each band receives at least
10% of the total observing time.
6) Can you place constraints on the cadence for deep drilling fields?
Example: In order to obtain good light-curve templates for SNe, at least one deep drilling field
has to be observed each night in all 6 bands for at least 4 months.
7) Assuming two visits per night, should they be obtained in the same band or not?
Example: The completeness considerations for asteroids suggest that two visits in a given
night should be obtained with the same band.
8) Would your science benefit from a special cadence prescription during commissioning or
early in the survey, such as: acquiring a full 10-yr count of visits for a small area (either in all or in selected bands); a greatly enhanced cadence for a small area?
Example: The deep drilling fields with multi-wavelength data would enable early science results
if LSST data were obtained early.
9) Do you have constraints for sampling of observing conditions (e.g. seeing, dark sky,
airmass), possibly as a function of band, etc.?
Example: Weak lensing science would greatly benefit if the r and i band data were obtained during the best seeing nights.
10) Do you have science drivers that would require real-time exposure time optimization
to obtain nearly constant single-visit limiting depth?
Example: Science programs requiring a minimum single-visit depth (such as Near-Earth Object
survey) would benefit from its uniform distribution.
Finally, if your science would benefit from a cadence methodology not covered by these questions,
please enter a description of this methodology at http://ls.st/yqq