1 WFC3 Science Data Volume  Data Volume Estimates for WFC3 Operations ISR WFC ; Lisse, Henry, Knezek, Hanley; 3/27/2001 ISR WFC ; Lisse, Henry, Knezek, Hanley; 3/27/2001  Data Volume per WFC3 exposure UVIS Channel Full frame image = 4140 x 4206 pixels (including overscan) = 266 Mbits/exposure IR Channel Full frame image = 1024 x 1024 pixels (including reference pixels) = 16 Mbit/image

2 WFC3 Primary Data Volume  Observing time allocation assumptions One third of orbits are used for spectroscopy and two thirds for imaging Imaging is divided evenly between WFC3 and ACS (5 orbits/day each) 60% of WFC3 primary orbits will use the UVIS channel (3 orbits/day) 40% of WFC3 primary orbits will use the IR channel (2 orbits/day)  WFC3 ETC was used to determine the number of exposures per orbit for each filter used in 41 DRM proposals UVIS exposures assumed CRSPLIT = 2 Number of exposures per orbit was limited to 10 for UVIS and 17 for IR based on the transfer rate out of the WFC3 data buffer and a 60 minute visibility period

3 WFC3 Primary Data Volume  Summary of exposure statistics UVISIR Total number of exposures42,36129,053 Total number of orbits9,7395,140 Average exposures/orbit  Primary UVIS data volume 266 Mbits/exp * 4.4 exp/orbit * 3 orbits/day = 3461 Mbits/day  Primary IR data volume Average number of nondestructive readouts = 10 Average data volume per exposure = 16 Mbits/image * 10 images/exp 160 Mbits/exp * 5.7 exp/orbit * 2 orbits/day = 1808 Mbits/day

4 WFC3 Parallel Data Volume  Assume WFC3 is in parallel for all non-prime orbits 30% of WFC3 parallel orbits will use the UVIS channel (3 orbits/day) 70% of WFC3 primary orbits will use the IR channel (7 orbits/day) Assume an average of 2 exposures per parallel orbit for UVIS and IR  Parallel UVIS data volume 266 Mbits/exp * 2 exp/orbit * 3 orbits/day = 1596 Mbits/day  Parallel IR data volume Average number of nondestructive readouts = 16 Average data volume per exposure = 16 Mbits/image * 16 images/exp 256 Mbits/exp * 2 exp/orbit * 7 orbits/day = 3584 Mbits/day

5 WFC3 Calibration Data Volume  Routine calibration exposures performed during occultations UVIS IR Internal Flats Earth Flats Dark Frames Bias Frames 104 Total per cycle Exposures/day  Calibration UVIS data volume 266 Mbits/exp * 3.6 exp/day = 950 Mbits/day  Parallel IR data volume 256 Mbits/exp * 2.2 exp/day = 568 Mbits/day

6 WFC3 Average Data Volume UVISIR Exp/dayMbits/dayExp/dayMbits/day Primary Parallel Calibration Total  Combined WFC3: 50 Exp/day11.7 Gbits/day

7 Post SM4 Average Data Volume PrimaryParallelCalibrationTotal WFC ACS COS STIS Total Average daily data volume in Gbits without overheads Average daily data volume in Gbits without overheads

8 Average Data Volume Trend (Gbit) PrimeParCalDailyWeekly (w overheads) SM SM SM  190 Gbit/week is 80% of the 245 Gbit maximum using one transmitter  Test SMSs with 150 Gbit of science data have shown the feasibility of scheduling at 60% of TDRSS capacity using both HST SSRs to buffer data (High data Volume SMSs and TDRS Contact Usage, Patterson et al, 5/18/200)  Using two HST transmitters raises maximum weekly downlink to 440 Gbit but transmitter lifetime concerns make operating in this mode undesirable.