【HST】 What is dataset and how to calculate for HST

The STScI final combined drizzled images and weight maps will consist of one dataset per filter per pointing per cluster = (3 ACS filters + 4 WFC3/IR filters) x 2 pointings x 6 clusters = 84 datasets total. 

The raw datasets are the number of visits x the number of filters/cameras per visit. 

Each pointing will have 35 visits per camera. Each visit will be 2 orbits long with a single filter per camera. See the table below (last question) for the number of orbits per filter/camera.

#  from : http://archive.stsci.edu/hst/bigsearch_request.html

There shows two different ways to define the DATASETS. In the first one, you consider one dataset to be one final drizzled image. You will have one dataset per filter per pointing per cluster. In the second way, which is the raw datasets, you define the datasets with the raw data. One dataset will be the one observation in one visit.

I use the definition of the raw datasets, which are the number of visits x the number of filters/cameras per visit, to calculate the number of datasets. (I found the definition of datasets from frontier field website: http://www.stsci.edu/hst/campaigns/frontier-fields/hstff_faq. See the question 4.).

Each visit will be 2 orbits long with a single filter per camera. Two ~1300s exposures per orbit per filter.  So I collect the exposure time from my pipeline and convert the exposure time to the number of datasets by dividing 2600 seconds for CLASH observations.

For frontier observations I just use the observation information from the website to calculate the number of datasets.

_________________ _________________ The results _________________ _________________

CLASH:

total exposure time:  1250669.68 seconds

dataset 481

FRONTIER:

Data are based on the website: http://www.stsci.edu/hst/campaigns/frontier-fields/HST-Survey

(140 orbit per cluster)/2 (orbits per visit ) x 6 (clusters) = 480 dataset

For circle 21/22 only:

(560 orbits in Cycles 21/22) / 2 (orbits per visit )  * 2 (cluster field + parallel field)= 560 dataset

_________________ _________________ _________________ _________________

### attached information

1. What are the Frontier Field clusters?
   All six cluster fields have been chosen. These are MACS0717.5+3745, Abell 370, Abell 2744, MACS0416.1-2403, MACSJ1149.5+2223 and RXCJ2248.7-4431.
2. Which clusters will be go first?
   The first year of observations will be of Abell 2744 and MACSJ0416.1-2403, the second year observations will be of MACSJ0717.5+3745 and MACSJ1149.5+2223, and contingent upon the success of the first two years of observations, the third year observations will be of RXCJ2248.7-4431 and Abell 370.
3. What filters and exposure times are planned?
   We will observe the same filter set to the same depths for both the cluster and blank field positions.
   The current planned orbital breakdown is:
   • ACS/WFC:
     • F435W - 18 orbits
     • F606W - 10 orbits
     • F814W - 42 orbits
   • WFC3/IR:
     • F105W - 24 orbits
     • F125W - 12 orbits
     • F140W - 12 orbits
     • F160W - 22 orbits
   • Two ~1300s exposures per orbit per filter. Two orbits per visit.
   These exposures are expected to reach ~5-sigma SNR for a point source with total aperture-corrected ABmag ~28.7-29.0. (See Table 2-4 in HDFI SWG report for details).
   The orbit allocation across the filters may be tweaked to account for field variation in Galactic extinction, and have not been finalized.
4. Here are the numbers for the duration of each observing window and their separation, based on a *preliminary* schedule.

   Cluster	Window 1	Window 2	Start of Window 1 - Start of Window 2
   Abell 2744	48 days	59 days	200 days
   MACSJ0416.1-2403	34 days	40 days	200 days
   MACSJ0717.5+3745	76 days	69 days	146 days
   MACSJ1149.5+2223	56 days	63 days	156 days
   RXCJ2248.7-4431	46 days	50 days	200 days
   Abell 370	69 days	69 days	220 days

   So the main cluster field will have 70 orbits of WFC3/IR observations spread out over 40-70 days, then 70 orbits of ACS/optical observations spread out over 40-70 days ~5-7 months later.