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
1
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
2
WFC3 Primary Data Volume

Summary of exposure statistics
Total number of exposures
Total number of orbits
Average exposures/orbit

UVIS
42,361
9,739
4.4
IR
29,053
5,140
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
3
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
4
WFC3 Calibration Data Volume


Routine calibration exposures performed during occultations
Internal Flats
Earth Flats
Dark Frames
Bias Frames
Total per cycle
UVIS
693
300
208
104
1305
IR
303
300
208
Exposures/day
3.6
2.2
811
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
5
WFC3 Average Data Volume
UVIS
Exp/day Mbits/day
Primary
13
3471
Parallel
6
1596
Calibration 3.6
950
Total
22.6
6017

Combined WFC3:
50 Exp/day
IR
Exp/day Mbits/day
11.3
1808
14
3584
2.2
568
27.5
5960
11.7 Gbits/day
6
Post SM4 Average Data Volume
WFC3
ACS
COS
STIS
Total
Primary
5.2
3.8
0.4
0.2
9.6
Parallel
5.1
5.1
0
0.1
10.3
Calibration
1.5
1.0
0.2
0.1
2.8
Total
11.7
9.9
0.6
0.4
22.6
Average daily data volume in Gbits without overheads
7
Average Data Volume Trend (Gbit)
Prime
2.1
5.0
9.6
SM2
SM3
SM4
190
Par
1.8
8.3
10.3
Cal
1.5
3.2
2.8
Daily
5.3
16.5
22.6
Weekly (w overheads)
48
150
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.
8