PFIS/ IMPALAS Issues

1. PFIS/ IMPALAS Issues • Outside Reviewer's Comments • Post-PDR tasks • Valuation Issues SALT PFIS Preliminary Design Review

2. Outside Reviewers Comments • The PFIS team is to be commended for conceptualizing a viable and all-encompassing solution to matching the PFIS science drivers to instrument performance and functionality. PFIS covers very effectively much observational science that remains largely unaddressed by the other large telescope projects inevitably resulting in a relatively complex, heavy and expensive instrument. • We agree of course! Important to us is that this endorses the particular niches that we originally proposed in the Concept Proposal, which drove the design. SALT PFIS Preliminary Design Review

3. Comments (cont) • We encourage the PFIS team to do as much to reduce the weight of PFIS as far as practical and be prepared to abandon thoughts of a double-beam instrument. • A weight reduction effort and reassessment of the mass budget is part of the post-PDR tasks. • We don't see abandonment of the second beam as being likely or necessary since we have shown that a second beam with a mass budget as large as the visible beam (140 kg) can be accommodated with a delta in mass for the whole instrument of 50 kg (because 90 kg of ballast is removed with addition of the second beam). • The second beam as currently configured is not a strong driver of the visible beam • A major redesign of a one beam instrument (perhaps to save additional weight) is unnecessary and not cost effective SALT PFIS Preliminary Design Review

4. Comments (cont) • We advise that any NIR spectroscopic capability be analyzed in enough detail that the SALT community is aware of its thermal/wavelength limitations and, if supported, is designed as a swap-in instrument. • Design of the second beam is out of scope for the current project. Some other team should investigate the claim that uncooled infrared spectroscopy is confined to wavelengths less than 1.4 microns, rather than the 1.7 microns used in the PFIS IR upgrade path description. Extending the PFIS collimator from 1.4 to 1.7 microns is not a driver for the PFIS instrument. • The upgrade path does not specify what the IR beam should do, it just enables a simultaneous beam that may be anywhere below 1.7 microns SALT PFIS Preliminary Design Review

5. Comments (cont) • The team should re-evaluate PFIS performance metrics (eg: spectral resolution) in the context of a more realistic ~1.5” slit-width régime. • We have been careful to specify that the resolutions given are for a slit width with the FWHM median seeing, which is common practice in spectrograph literature. It is a valid criticism that common practice is not conservative enough, since such a slit width entails substantial slit loss. • 1.5 arcsec would give seeing-limited resolution, which we do not believe is the optimum for most programs like • Work on unresolved spectral features (this is why you want resolution! • Background-limited work (very important for large telescope with large images) • In future literature we will endeavor to specify slit losses with median and best seeing for the slit width specified. SALT PFIS Preliminary Design Review

6. Comments (cont) • The mechanical design presented was not judged to be at the expected level for a PDR. This contrasts with the impressive volume of paper work presented. • We don't know how to respond to this, since the nature of the deficiency is not described. SALT PFIS Preliminary Design Review

7. Comments (cont) • A 15% contingency is much too small for the PDR phase given PFIS’ complexity. We see a serious deficiency in the detailed planning and budgeting and would encourage the project to identify professional project management resources to establish more secure costings particularly in the staff and optics procurement areas. • An independent cost estimate is welcomed. We felt we benefited greatly from the independent Swales mechanical costing exercise. • Three more quotes are due soon from optics manufacturers • It is not clear which kind of staffing is deemed to be insufficient SALT PFIS Preliminary Design Review

8. Post PDR tasks • Open ends to be resolved in next 6 weeks (scheduled system conceptual design final iteration) • slitviewer proposal • resolution of mass property budget • definition of interfaces • structure iteration to remove flexure trouble spots • waveplate configuration SALT PFIS Preliminary Design Review

9. Valuation - Baseline Base Dollars 3,646,000 The only way of decreasing the baseline cost • Design phase descoping, eg • Field of View at camera (3 -> 2 chips) • Chips -$50K (note: need to do this immediately!) • Optics -$25K - -$50K • redesign +$40K (4 weeks) • Net -$35K to -$60K: Again, Save very little, with significant loss of resolution elements • Beam size 150 mm -> 116 mm • etalons -$21K • optics -$25K - $75K • redesign +$60K (6 weeks) • Net +$14K - -$36: Save very little, if anything, with significant loss of resolution SALT PFIS Preliminary Design Review

10. Valuation - Baseline • Fabrication Phase descoping • third etalon -$~120K • quarterwave plate -$71K • slitmask factory -$106K • Total -$297K • These purchases will be delayed as long as possible in case of contingency overrun. • Could be used to replace contingency: "descope as you go" Base Dollars SALT PFIS Preliminary Design Review

11. Valuation - Contingency Base Dollars 3,943,000 • PDR budget contingency • 15% on all purchased items, except CCD's and etalons (firm quotes) • 3 months manpower in CDR phase and in Fabrication Phase. Would be applied by hiring help, if schedule is firm, or by stretching schedule, if it is not • Suggest valuation at the baseline value, with increases within the contingency budget if necessary, approved by Project Scientist • Possible cost savings transferred to contingency (eg CCD) SALT PFIS Preliminary Design Review