1. SciReq
  2. History
  A B C D E F G H I
1 Science Requirements and System Specifications                    
2 Version: 24                        
3                            
4 Science Estimates                        
5                            
6 Stars in Universal Sky + Galactic Plane                      
7 mag limit u g r i z y coadd (for a given r mag)          
8 21.5           3.38E+09   All numbers assume an SRD-like cadence and nominal sky coverage    
9 22.5 3.70E+08 1.07E+09 2.15E+09 3.54E+09 5.01E+09 6.20E+09              
10 23.5 6.10E+08 1.68E+09 3.41E+09 5.82E+09 8.50E+09 1.07E+10              
11 24.5 9.44E+08 2.52E+09 5.17E+09 9.15E+09 1.36E+10 1.67E+10 6.93E+09            
12 25.5 1.39E+09 3.67E+09 7.59E+09 1.36E+10 1.91E+10 2.03E+10 1.10E+10            
13 26.5 1.97E+09 5.23E+09 1.07E+10 1.87E+10 2.06E+10   1.66E+10            
14 27.5 2.75E+09 7.33E+09 1.45E+10 2.07E+10     2.04E+10            
15 28.5             2.07E+10            
16 29.5             2.07E+10            
17                            
18 Stars in Universal Sky Only                        
19 mag limit u g r i z y coadd (for a given r mag)          
20 21.5           1.59E+09              
21 22.5 2.81E+08 6.91E+08 1.18E+09 1.74E+09 2.26E+09 2.59E+09              
22 23.5 4.35E+08 1.01E+09 1.71E+09 2.61E+09 3.43E+09 3.89E+09              
23 24.5 6.28E+08 1.41E+09 2.41E+09 3.72E+09 4.71E+09 5.17E+09 2.99E+09            
24 25.5 8.65E+08 1.94E+09 3.29E+09 4.88E+09 5.74E+09 5.97E+09 4.19E+09            
25 26.5 1.17E+09 2.65E+09 4.30E+09 5.81E+09 6.17E+09   5.35E+09            
26 27.5 1.56E+09 3.52E+09 5.25E+09 6.24E+09     6.08E+09            
27 28.5             6.27E+09            
28 29.5             6.29E+09            
29                            
30 Single Frame Depth                        
31 Mag limit 24 25.1 24.8 24.1 23.4 22.2   Stretch goals from SRD        
32 US+GP Stars 7.59E+08 3.16E+09 5.80E+09 7.63E+09 8.06E+09 5.17E+09              
33                            
34                            
35 Stars 8.22E+08 3.42E+09 6.29E+09 8.27E+09 8.74E+09 5.60E+09   including uncertainty and survey area      
36 Galaxies 8.04E+08 3.02E+09 3.12E+09 2.33E+09 1.93E+09 8.73E+08   (based on galaxies @end so includes uncertainty and survey area)    
37                            
38                            
39 End of Survey                          
40 Galaxies                          
41 dLogNdMag 0.39 0.32 0.3 0.31 0.31 0.34              
42 Tot Galaxies 6.01E+00 1.77E+01 2.24E+01 1.79E+01 1.40E+01 7.74E+00 2.33E+10            
43 Total 6.51E+09 1.92E+10 2.42E+10 1.93E+10 1.52E+10 8.39E+09 2.52E+10 including uncertainty and survey area      
44                            
45 Epochs 73 102 236 236 205 205 1057            
46 Star Sources 6.00E+10 3.49E+11 1.48E+12 1.95E+12 1.79E+12 1.15E+12 6.78E+12            
47 Gal Sources 5.87E+10 3.08E+11 7.37E+11 5.50E+11 3.96E+11 1.79E+11 2.23E+12            
48 Sources 1.19E+11 6.57E+11 2.22E+12 2.50E+12 2.19E+12 1.33E+12 9.01E+12            
49                            
50 Nominal survey area 30,000 sq deg                    
51 Star uncertainty   30%                      
52 Galaxy uncertainty 30%                      
53                            
54 Growth Curves                          
55 Year Gal Objects r Band Limit Star Objects US Stars Objects Sources ForcedSrcs            
56 0.5 7.91E+09 26.0 1.47E+10 5.14E+09 2.26E+10 4.51E+11 1.20E+12            
57 1 1.03E+10 26.4 1.71E+10 5.63E+09 2.75E+10 9.01E+11 2.91E+12            
58 2 1.35E+10 26.8 1.90E+10 5.99E+09 3.25E+10 1.80E+12 6.87E+12            
59 3 1.58E+10 27.0 1.98E+10 6.16E+09 3.57E+10 2.70E+12 1.13E+13            
60 4 1.77E+10 27.1 2.05E+10 6.29E+09 3.82E+10 3.60E+12 1.61E+13            
61 5 1.93E+10 27.3 2.10E+10 6.39E+09 4.03E+10 4.51E+12 2.13E+13            
62 6 2.07E+10 27.4 2.15E+10 6.47E+09 4.22E+10 5.41E+12 2.67E+13            
63 7 2.20E+10 27.4 2.18E+10 6.54E+09 4.38E+10 6.31E+12 3.24E+13            
64 8 2.32E+10 27.5 2.21E+10 6.59E+09 4.53E+10 7.21E+12 3.83E+13            
65 9 2.42E+10 27.6 2.21E+10 6.61E+09 4.64E+10 8.11E+12 4.41E+13            
66 10 2.52E+10 27.6 2.21E+10 6.62E+09 4.74E+10 9.01E+12 5.01E+13            
67                            
68                            
69 Description           Value Unit Notes          
70 Increase in the log of number of galaxies per magnitude     0.31   Science Book number for galaxies (Equation 3.7).      
71 Peak number of alerts per visit         40,000   Between SRD minimum of 10K and stretch of 100K      
72 Average number of alerts per visit due to variables and old transients     10,000   SRD design spec        
73 Average number of alerts per visit due to new transients     100              
74 Average number of alerts per visit due to false positives     5,050   50% of real alerts        
75 Number of moving objects         6,000,000   Table 5.1 in the Science Book        
76 Fraction of all DiaSources from moving objects       16.00%              
77 Time window for forced photometry of transient DiaObjects before and after first DiaSource 2.02 months 1 month before, 1 month of normal DiaSources, 1 month after for new transients, 1 month before/after for false positives
78                            
79 Camera Specifications                        
80                            
81 Description           Value Unit Notes          
82 Area of single exposure         9.6 sq deg            
83 Pixels per image (billions)         3.56552582 gigapixels 189 CCDs of 16 amplifiers of 562x2098 pixels (including overscan)    
84 Number of filters           6              
85 Number of CCDs           189              
86 Number of amplifiers per CCD         16              
87 Number of CCDs for wavefront data         4              
88                            
89 Survey/Cadence Specifications                      
90                            
91 Description           Value Unit Notes          
92 Expected sky area surveyed         25,000 sq deg OSS, includes special programs        
93 Total visits           2,750,000 visits OpSim estimate + 10% margin        
94 Epochs (average visits to any object/area)       1,056 visits            
95 Survey length           10 years OSS          
96 Observing nights per year         298.35 nights Can be up to 351 if weather is excellent and no unscheduled down time; assumed mean from OSS is (365-14-14)*.85 = 286, though. Omitted unscheduled downtime from number here to be conservative.
97 Worst-case mean exposure time including slew       18 sec Assumes slew is less than 2 sec readout (derived from OSS-REQ-0189)  
98 Images (exposures) per visit         2              
99 Observing time per night (average)         10 hours            
100 Observing time per night (peak)         14 hours            
101 Number of raw calibration images per 24 hours       503   Calibration Plan and OSS (dividing number per year by observing nights, though some are taken during non-observing)
102                            
103 Filter Min # epochs # epochs                      
104 U 57 73           Min epochs from SRD        
105 G 80 102                      
106 R 184 236                      
107 I 184 236                      
108 Z 160 205                      
109 Y 160 205                      
110 avg 138 176.17                      
111 sum 825 1,057                      
112                            
113                            
114 Engineering & Facility Database Specifications                    
115                            
116 Description           Value Unit Notes          
117 Size of E&F telescope images incl spectra per day       234 GB            
118 Size of E&F summary data per day         8.2 GB            
119 Size of DM systems operational status per day       0.01 GB 10MB          
120                            
121                            
122 Network Requirements                        
123                            
124 Description           Value Unit Notes          
125 Mountain to Base:                        
126 Time to transfer 1 x-talk corrected image       2 sec time to tranfer raw image: exposuretime – 2      
127 Time to transfer E&F data for 1 image       1 sec            
128 Burst capacity to catch up         200%              
129 Buffer size at Mountain Top for network failures       2 days of maximum length nights        
130 Bandwidth for transfering ops information data (commands, status, monitoring)   100 Mbits/sec provided by German Schumacher, May 17, 2011      
131 Base to Archive:                        
132 Time to transfer all raw images (per 24h)       43,200 sec 12h          
133 Burst capacity to catch up         400%              
134 Buffer size at Base for network failures       14 days of maximum length nights        
135 Archive to Base:                        
136 Time to transfer calibration products (master calibration images) monthly   21,600 sec 6h          
137 Time to transfer calibration products (master calibration images) pre-DR     86,400 sec 24h          
138 Time to transfer db catalogs produced by DR       2,592,000 sec 30 days          
139 Time to transfer templates and co-adds produced by DR     5,443,200 sec ½ of DR length          
140                            
141 Image Storage Requirements                      
142                            
143 Description           Value Unit Notes          
144 Raw images:                          
145 Number of most recent visits kept on disk for each FOV for each filter     2 visits            
146 Equivalent number of nights of observing during Commissioning     93 nights 3 months with full camera, 2 months with single-raft camera (5%)    
147 Equivalent number of days of calibrations during I&T and Commissioning   315 days 1 year with full camera, 1 year with single-raft camera (5%)    
148                            
149 Raw calibration images:                        
150 Number of nights' worth of raw calibration images kept on disk     30 nights            
151                            
152 Calibrated images:                        
153 Number of nights' worth of recent calibrated images kept on disk     30 nights            
154 Number of nights' worth of old cached calibrated images     6 nights For all others requested on demand      
155                            
156 Co-adds and templates:                        
157 Increased pixel density factor for co-adds/templates       2   areal density, sqrt(2) in each dimension      
158 Extra bits to represent co-add depth value       16 bits            
159                            
160 Co-added images:                        
161 Number of releases of co-added images kept on disk       2 releases            
162 Number of types of co-adds (e.g, one per filter, etc)       8 types one per filter plus one chi-squared pan-chromatic detection plus small samples of other types
163                            
164 Templates:                          
165 Number of releases of template images kept on disk at Archive Center     1 releases only most recent template from last DR      
166 Number of versions of templates (e.g. for different airmasses)     3 versions            
167 Number of types of templates (e.g, one per filter, etc)       6 types            
168                            
169 Master calibration images:                        
170 Number of per-filter images used at one time       4 images flat, fringe frame, scattered light correction, illumination correction    
171 Number of per-filter flat images (only one used at a time) in a set     18 images every 20 deg of rotation        
172 Number of per-filter images in a set for storage       21 images            
173 Number of filter-independent images in a set       3 images bias, dark, bad pixel mask        
174 Frequency of updates per six months       6 updates            
175 Number of releases of MCI kept on disk       4 releases see Storage Estimates imgData P18-T30 when changing this number    
176                            
177 Engineering & Facility Database:                      
178 Number of releases of E&F telescope images kept on disk     3 releases 1 for latest epoch + 2 for coadds        
179                            
180                            
181 Data Release Production Specifications                      
182                            
183 DR definition, new deep det, templates, master calibration images                          
184 yr 6m 6m data sets DR number DR number DR MC img Co-add sets Template sets          
185   elapsed for given DR released given yr under constr Length (years) (6m sets) Generated Generated          
186 1 1 1 1 1 0.5 1 1 1          
187 1 2 2 2 2 0.5 2 1 1          
188 2 4 4 3 3 1 4 1 2          
189 3 6 6 4 4 1 6 1 3          
190 4 8 8 5 5 1 8 1 4          
191 5 10 10 6 6 1 10 1 5          
192 6 12 12 7 7 1 12 1 6          
193 7 14 14 8 8 1 14 1 7          
194 8 16 16 9 9 1 16 1 8          
195 9 18 18 10 10 1 18 1 9          
196 10 20 20 11 11 1 20 1 10          
197   When changing DR definition, change Storage Estimates dbData X104:AE117                
198   if DR takes multiple years, the “under constr DR number” is the number of DR that is currently under construction            
199                            
200 copy this for stretched DR scenario:                      
201 1 1     1 1 1 2 1          
202 1 2 1 1 1 1 1 1 1          
203 2 4 2 2 2 1 2 1 1          
204 3 6     3 2 2 1 2          
205 4 8 4 3 3 2 2 1 2          
206 5 10     4 2 2 1 3          
207 6 12 8 4 4 2 2 1 3          
208 7 14     5 2 2 1 4          
209 8 16 12 5 5 2 2 1 4          
210 9 18     6 2 2 1 5          
211 10 20 16 6 6 2 2 1 5          
212                            
213 Description           Value Unit Notes          
214 Data Release Production Sequencing:                      
215 Time for Calibration Preparation         2 weeks            
216 Time for CSI+SFM         18 weeks            
217 Time for Coaddition         18 weeks            
218 Time for Object Characterization + ForcedSource Measurement     18 weeks            
219 Time for Astrometric Calibration         4 weeks            
220 Time for Photometric Calibration         4 weeks            
221 Time for Image Differencing         18 weeks            
222 Time for MOPS           18 weeks            
223 Time for EPO JPEG generation         2 weeks            
224                            
225 Time for major Data Release pipeline components       18 weeks            
226                            
227 Data Release Production Parameters:                      
228 Average coadd depth for templates         5 images Doesn't need to be much deeper than single frame      
229 Times each image is used for deep coadds       4   Once for per-filter, weighted average of three times more for other coadds  
230 Number of astrometric calibration parameters per object     10              
231                            
232                            
233 Calibration Products Production Specifications                    
234                            
235 Description           Value Unit Notes          
236 Size of calibration database per 6 months (uncompressed, just the data, not counting index) 0.5 TB            
237                            
238                            
239 User Image Access Specifications                      
240                            
241 Description           Value Unit Notes          
242 Fraction of all alert postage stamps accessed by users in 24h     1%              
243 Calibrated image cutout size         1 CCDs Update storage spreadsheet – otherInput.H36 when changing this    
244 Co-add/template image cutout size         1 CCDs Update storage spreadsheet – otherInput.H40 and H48 when changing this  
245 Low volume query output bandwidth       10 Gbit/sec            
246 Low volume query rate         66.3 simul queries            
247 Low volume query response time         10 sec            
248 Low volume query result size         0.189 GB            
249 High volume query rate         20 simul queries            
250 High volume query response time         60 sec 1 min          
251 High volume query result size         6 GB            
252                            
253 Low volume query mix:       Fraction Query Rate Cache Miss Notes          
254 Cutouts from coadds       26% 17.2 75%            
255 Cutouts from templates       10% 6.6 75%            
256 Cutouts from calibrated science images     62% 41.1 75%            
257 Master calibration images       2% 1.3 10% Effective query rate for all image types for calibration image queries    
258                            
259 High volume query mix:       Fraction Query Rate Cache Miss Notes          
260 Cutouts from calibrated science images     100% 20 50%            
261                            
262 Color jpeg                          
263 Simultaneous queries (ccd size)         10              
264 Response time per query         1 sec            
265                            
266 User Catalog Query Specifications                      
267                            
268 Description           Value Unit Notes          
269 Low volume query rate         100 simul queries More than 5 times SDSS SkyServer peak rate from astronomers    
270 Low volume query response time         10 sec            
271 Low volume query result size         0.5 GB            
272 High volume query rate         56 simul queries Of differing latencies        
273 Target average high volume query throughput       20 per hour            
274 Modeled high volume query throughput       20 per hour            
275 High volume query result size         6 GB            
276                            
277 Number of data releases served         2   latest, latest-1. If you change this number, change formulas in Storage Estimates dbData W105-AC119
278 Spatial sample of previous data releases kept on disk       5%              
279 Continuous Object (narrow) scan length in hours (scan through latest data release only)           1              
280 Continuous Object (narrow) scan average simultaneous queries           16              
281 Continuous Source+Object (narrow) scan length in hours (latest data release only)           12              
282 Continuous Source+Object (narrow) scan average simultaneous queries           12   To generate an average throughput of one per hour      
283 Continuous ForcedSource+Object (narrow) scan length in hours (latest data release only)           12              
284 Continuous ForcedSource+Object (narrow) scan average simultaneous queries           12   To generate an average throughput of one per hour      
285 Additional continuous Object scans for high-volume queries (one on each DR)           2   With extra joined tables including Object (wide) as needed    
286 Additional Object scan length in hours (target)           8   Can be longer if more tables joined        
287 Additional Object scan average simultaneous queries (per scan)           8   To generate an average throughput of one per hour per scan    
288                            
289 Fraction of low-volume query traffic on Object table           70%   This involves Object-only based low volume queries as well as traffic to Object table for low-volume queries that involve Object-Source and Object-ForcedSource joins
290 Fraction of low-volume queries on Source table           20%              
291 Fraction of low-volume queries on ForcedSource table           10%              
292                            
293 Low volume queries:                          
294 Class “A” (single object fetch) fraction           5%              
295 Class “B” (few objects fetched) fraction           60%              
296 Class “C” (small area fetched through index) fraction           25% area: 0.25          
297 Class “D” (small area fetched through partition scan) fraction           10% area: 1          
298                            
299 Number of low volume queries for the L1 Database       20 simul queries            
300 Number of low volume queries for E&FD (accessing catalog and image data)   5 simul queries            
301                            
302                            
303 L3 Processing Specifications                      
304                            
305 Description           Value Unit Notes          
306 Minimum fraction of total compute for L3 Service Level 1     10%              
307 Minimum fraction of total compute for L3 Service Level 2     2%              
308 User accounts for DB space and general disk space       7500 users            
309 Disk space per user         1 TB            
310 DB space per user         0.5 TB            
311 Oversubscription factor         0.25   On average each user consumes only this much allocated space    
312                            
313 EPO Specifications                        
314                            
315 Description           Value Unit Notes          
316 Number of streams (such as EPO) that will read alert postage stamps at one site   2              
317 Time to read alert postage stamps for EPO       900 sec 15 min          
318                            
319 Common Constants and Derived Values                      
320                            
321 Useful Constants                        
322                            
323 Description           Value Unit Notes          
324 Bits per byte 1000         8 bits            
325 KB (kilobyte)           1.02E+03 bytes            
326 MB (megabyte)           1.05E+06 bytes            
327 GB (gigabyte)           1.07E+09 bytes            
328 TB (terabyte)           1.10E+12 bytes            
329 PB (petabyte)           1.13E+15 bytes            
330                            
331 Thousand (kilo) 1000         1.00E+03              
332 Million (mega)           1.00E+06              
333 Billion (giga)           1.00E+09              
334 Trillion (tera)           1.00E+12              
335 Quadrillion (peta)           1.00E+15              
336 Quintillion (exa)           1.00E+18              
337                            
338 Seconds per hour         3,600 sec            
339 Seconds per day (24 hours)         86,400 sec            
340 Seconds per week         604,800 sec            
341 Seconds per month (30 days)         2,592,000 sec            
342                            
343 Common Derived Values                        
344                            
345 Description           Value Unit Notes          
346 Survey area in equivalent fields-of-view       2,604              
347 Fraction of objects observable in single visit (cadence-weighted average)   0.00              
348 Images per night (average)         2,000              
349 Images per night (peak)         2,800              
350 Visits per night (average)         1,000              
351 Size of image (16 bit)         0.006964 TB            
352 Size of image (32 bit)         0.013928 TB            
353 Size of image (coadd depth portion)       0.006964 TB            
354 Size of one calibrated science image (data, variance, mask)     0.034820 TB            
355 Size of one set of template images in one filter       218 TB            
356 Size of a section of a calibrated science image for cutout generation     0.000184 TB            
357 Size of a section of a template/co-add for cutout generation     0.000442 TB            
358 Ratio of wavefront to raw         0.021164              

Back to top

  A B
1 24  
2    
3 24 Updated raw calibration images to match Calibration Plan/OSS yearly number; reduced raw calibration queries to fit bandwidth constraint.
4 23 Added parameters for I&T and Commissioning image storage.
5 22 Updated object/source counts, removed visibility percentage, reduced sky area to 25K sq deg, reduced visits to 2.75M
6 21 Add ForcedDiaSource time window, change worst-case mean exposure time, increase transient false positives, improve documentation
7 20 Compute star objects by year from r-band magnitude, increase peak alerts, include overscan pixels, fix min epochs to match SRD, update query specifications, cadence-weight objects per visit, add source notes, fix descriptions
8 19 Redid change in v17, updated raw calibration images number
9 18 Major changes related to Data Products Definition and new Data Access requirements
10 17 Added #ccds for wavefront (new rows: 98, 362)
11 16 Added time to transfer L1 data from Archive Site to Base Site (new row 153)
12 15 Changes related to moving AP from Base Site to Archive Site (moved a row into a new section)
13 14 Changed Source scan frequency from 1 in 8h to 1 in 16h
14 13 Update to object/source/forcedsource model, total visits
15 12 Changed pixel density for templates/coadds from 4 to 2. Increased number of templates on disk from 4 to 5. Changed survey area from 18 to 20 K. Adjusted area for db low vol query class C
16 11 changed the frequency back to 1/week
17 10 changed frequency of shared scans for forced source from 1/week to 1/day
18 9 changed timing for mountain/base transfer of x-talk and raw images
19 8 added jpeg queries – new rows (212-214)
20 7 number of visits changed from 824 to 825 to realign with SRD
21 6 Decrease percentage of DIASources attributed to moving objects
22 5 hv db queries: ratios changed: obj-related increased. Changes alerts/visit 2K to alerts/night 2million
23 4 increased number of stars and galaxies by 30% (due to uncertainties)
24 3 changing number of templates to 4 (as it was in the storage spreadsheet). Using version “3” to sync with Docushare numbering
25 1 Initial version (June 28, 2011)

Back to top