STUDY SUMMARY - IPMU

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<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) ance, or 3) added risk. A list of descopes and trigger dates will be used to balance any cost overruns within the framework of balancing risk in the instrument. The most important feature of this approach is to implement the descope in a timely manner. Features maintained in the descope list are: • Descope options, with implementation approach • The resulting acceptable reduced performance or risk position. • The schedule milestones related to the required decisions. • The budget impact if the options are exercised at the identified milestones. • The survey success impact. • Reserve Management. This strategy has been used successfully on other projects that have faced similar cost caps such as M3, recently delivered, and the Nuclear Spectroscopic Telescope Array (NuSTAR) project, currently in Phase C/D. A formal process that may include a trade study to review the impact and final approval from the management team is required to exercise the descope. The advisory board may be involved if the change is significant and Gemini will be consulted on any descope that affects a Level 1 or Level 2 requirement. The challenge is that the time to exercise a descope effectively is often early and there is a tendency to want to defer in order to maintain all features of the original design. A descope list will be developed further at the start of the study, but at this time two high-level descopes are to reduce total number of positioners and to use standard spectrograph CCDs instead of custom CCDs. For the positioners, there are several execution dates: 1) start of positioner contract, 2) parts procurement, 3) positioner assembly, and 4) bench assembly. At each stage, the cost savings decreases, but this allows the flexibility to maintain the baseline design as long as possible. We can also generate multiple trigger dates in the procurement of custom CCDs. Similarly, cost savings decrease with time, but the option retains the advantages of the system for as long as possible. Both of these descope options described effectively increase the survey time. Science goals are still achievable, but the instrument is less efficient. 75
<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) Item Use COTS CCDs instead of custom CCDs Reduce number of positioners from 2,400 to 1800 Reduce number of spectrographs from 3 to 2 Reduce the number of metrology cameras in JPL I&T Decision Date Project start, parts order, integration Positioner CDR, parts order, start of positioner integration Spectrograph CDR Metrology CDR, JPL I&T Table 7.2-4: Descope Options Likelihood of Performance Impact Performance Impact 30% reduction in wavelength coverage or resolution, depending on survey Decreased observing efficiency Decreased observing efficiency Decrease in throughput Other Subsystems Affected Cost Reduction High Spectrograph $260K High High Low Spectrograph, fibers, detectors Positioners, fibers, detectors Software, thermal system Comment $1.2M Coupled w/ reducing spectographs to 2. Costs only reflect reduction number of positioners. Additional savings in integration and test $2.5M Coupled w/ reducing number of postioners to 1800. $490K After early testing, it may be possible to go to one 4K x 4K camera. Additional error in measuring postioner locations results in loss of throughput 7.3 Schedule The baseline schedule is 58 months as shown in Figure 7.3-1. The baseline costs are developed against the 58-month schedule; project reserves are sufficient to cover development and build risk as well continuing workforce if schedule reserves, estimated at 5 months, are used. If the schedule reserves are used fully, the total project timeline is 63 months for a final delivery date of December 13, 2014. This schedule shows the critical path is through the fiber system. However there are two major paths leading to instrument integration; this schedule shows these two major tested subsystems delivering to the telescope within two months of each other. Some of the major milestones are: • Kickoff Meeting. • Project System Requirements Review (SRR). • Project and subsystem Preliminary Design Reviews (PDR). • Project and subsystem Critical Design Reviews (CDR). • Integration and Test Readiness Review. • Delivery of test slit blocks with fibers to the spectrograph. 76
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STUDY SUMMARY - IPMU

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