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WFC3 Science Data Volume

WFC3 Science Data Volume. Data Volume Estimates for WFC3 Operations ISR WFC3 2001-02; 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

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WFC3 Science Data Volume

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  1. WFC3 Science Data Volume • Data Volume Estimates for WFC3 Operations ISR WFC3 2001-02; 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 exposures 42,361 29,053 Total number of orbits 9,739 5,140 Average exposures/orbit 4.4 5.7 • 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 693 303 Earth Flats 300 300 Dark Frames 208 208 Bias Frames 104 Total per cycle 1305 811 Exposures/day 3.6 2.2 • 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 UVIS IR Exp/day Mbits/day Exp/day Mbits/day Primary 13 3471 11.3 1808 Parallel 6 1596 14 3584 Calibration 3.6 950 2.2 568 Total 22.6 6017 27.5 5960 • Combined WFC3: 50 Exp/day 11.7 Gbits/day

  7. Post SM4 Average Data Volume Primary Parallel Calibration Total WFC3 5.2 5.1 1.5 11.7 ACS 3.8 5.1 1.0 9.9 COS 0.4 0 0.2 0.6 STIS 0.2 0.1 0.1 0.4 Total 9.6 10.3 2.8 22.6 Average daily data volume in Gbits without overheads

  8. Average Data Volume Trend (Gbit) Prime Par Cal Daily Weekly (w overheads) SM2 2.1 1.8 1.5 5.3 48 SM3 5.0 8.3 3.2 16.5 150 SM4 9.6 10.3 2.8 22.6 190 • 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.

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