A -- CONSTELLATION X-RAY MISSION PRECISION MANDRELS

Notice Date

December 19, 2000

Contracting Office

NASA/George C. Marshall Space Flight Center, Procurement Office, Marshall Space Flight Center, AL 35812

ZIP Code

35812

Solicitation Number

8-1-1-S7-D1127

Response Due

January 12, 2001

Point of Contact

Barry S. Kaigler, Contract Specialist, Phone (256) 544-0426, Fax (256) 544-9354, Email barry.kaigler@msfc.nasa.gov -- Warren G. Jones Jr., Contracting Officer, Phone (256) 544-0389, Fax (256) 544-9354, Email warren.jones@msfc.nasa.gov

E-Mail Address

Barry S. Kaigler (barry.kaigler@msfc.nasa.gov)

Description

This is a modification to the synopsis entitled [CONSTELLATION X-RAY MISSION PRECECISION MANDRELS, AND SOLICITATION NO. 8-1-1-S7-D1127] which was posted on [October 12, 2000]. You are notified that the following changes are made: [DESCRIPTION] THIS NOTICE SERVES AS OFFICIAL THE AMENDEMENT TO SUBJECT SYNOPSIS/RFQ AND A WRITTEN AMENDMENT WILL NOT BE ISSUED. The purpose of this amendment is to provide official answers to questions received. The due date for receipt of [bids/offers/quotes] [is] extended [January 12, 2001]. 1. QUESTION: Section B . 3. c. / Focal length The tolerance for the focal length at 20 0C is specified to be +/ -- 0.5 mm for all mandrel configurations A to F. After having reviewed this requirement (tolerance/error budget) we found that this specification can not be met with our existing (proven) metrology equipment . We therefore request a relaxation of the focal length tolerance (at 20 0C) as follows : for configuration A (D) : +/- 2.0 mm for configuration B (E) : +/- 2.5 mm for configuration C (F) : +/- 3.0 mm ANSWER: Section B.3.c. Focal Length We reviewed the error budget and determined that the flight system will probably require control of the focal length at a level only slightly less restrictive than that stated in the Specification / Statement of Work. Thus, we anticipate the following GOAL for the focal-length RMS ERROR: Configurations A and D (800-mm radius), +/- 0.8 mm; Configurations B and E (600-mm radius), +/- 1.0 mm; and Configurations C and F (500-mm radius), +/- 1.2 mm. Because these are not flight-system mandrels and because an RMS error has little meaning for one mandrel, we set the REQUIREMENT on the TOLERANCE to be 3 times the GOAL for the focal-length RMS ERROR of the flight system. Configurations A and D (800-mm radius), +/- 2.4 mm; Configurations B and E (600-mm radius), +/- 3.0 mm; and Configurations C and F (500-mm radius), +/- 3.6 mm. Consequently, we shall regard offers satisfying the above REQUIREMENT on this TOLERANCE to be responsive. 2. QUESTION: Section B. 3. d. / Width and Length of Optical Surfaces Separate mandrels : configurations D to F : It is requested that "separate P and H mandrels shall include either a precision alignment fixture or , at a minimum , precision reference surfaces and procedures for co -aligning the two portions to the accuracy needed to meet the performance specification . For the separate P and H mandrels ,when aligned , the polished and figured surfaces of P and H portions must be contiguous , such that the perfectly replicated monolithic P -- H mirror would satisfy the performance specification." We don't clearly understand these requirements . Is the intention to bild -- up from two separate mandrels (P and H ) a monolithic mandrel unit , delivering the same performance as an integral mandrel ? How shall the intersection area of P and H look like ?(gap allowed , how wide )? Please explain in more details what you expect from this configuration and how it should be built up. ANSWER: Section B.3.d. Width and Length of Optical Surfaces (Configuration of separate mandrels) In order to support replicated-segment development, we wish to retain the flexibility to replicate either integral-P-H or separate-P-and-H mirror segments from any of the mandrel configurations. Thus, the gap between the separate P and H mandrels should be small compared to the +/-25-mm band of relaxed performance. We would like this gap to be as small as possible consistent with other considerations, including Functionality (Section B.1.a.). However, we require that the gap not extend beyond +/-5 mm of the intersection plane. Furthermore, the band of relaxed performance includes this gap. 3. Question: Section B. 3. d. / Area of relaxed performance requirement It is written that " the performance requirements need not to be satisfied in a band < 25 mm2 on either side of the intersection plane " We believe that it must read : in a band < 25 mm (not mm square) on either side of the intersection plane. ANSWER: Section B.3.d. Width and Length of Optical Surfaces (Band of relaxed performance) The specification on the band of relaxed performance around the P-H intersection should be < 25 mm, not < 25 mm^2. 4. Question: Section B. 3. d. / Mandrel chord Fromig.2 , we extract that for all mandrel configurations the minimum chord at P -- H intersection shall be 420 mm. This corresponds for mandrel config. A and D ( R= 800 mm) to an optically useful segment angle of 30.40. We wonder if it's really intended by MSFC that the mandrels with smaller radius (config. B , C and E,F ) shall have increasingly larger segment angles ,driven by the constant chord of 420 mm. We ask this question as a constant segment angle for all mandrel configurations (our suggestion !) would lead to reduced chords and to reduced thicknesses of mandrels with smaller radius , which would make fabrication of such mandrels less expensive . Please let us know your position and your comments. ANSWER: Section B.3.d. Width and Length of Optical Surfaces (Mandrel chord length) We intentionally specified the chord length rather than the segment angle. Thus, any of the three mandrel sizes would allow replication of segmented optics of approximately the same physical size as the largest segment we would replicate. This would be a 419-mm arc-length (at intersection plane) segment, corresponding to a 30-degree segment of a 1.6-m diameter optic. Thus, the smaller-radius mandrels do indeed cover larger segment angles. In order to clarify this, we add the following: The design of the mandrels shall allow replication of P-H segments of length 1000 mm (500 mm per surface) and of the following minimum segment angles (over this entire length): Configurations A and D (800-mm radius), 30 degrees; Configurations B and E (600-mm radius), 40 degrees; and Configurations C and F (500-mm radius), 48 degrees. 5. QUESTION: In chapter B.3.b. /Tab.1 , the tolerances for the mandrel radius at the intersection plane are given to : +/- 0.01 mm ( = +/- 10 5m ) . We request that this requirement shall be deleted from the spec./SOW . Justification: 1)This requirement can not be checked (measured ) in practice , it could only be calculated by extrapolation of the tangents to the parabola and hyperbola sections. 2) In practice , it is not feasible to polish mandrels of such size in a reasonable time to such a small radial tolerance. From our point of view , a +/- 0.01 mm radius tolerance is a "fabrication overkill" . We believe , that , as long as the deviation of the "as made " mandrel radii from the "as designed" radii are within the error budget for a given focal length tolerance , we should be allowed to stay within such deviations. Typically , such radius deviations for CON -- X mandrels could be in the range of +/- 50 5m without violating the focal length error budget. We kindly ask you to check our request and to respond as soon as possible. ANSWER: Section B.3.b. Table 1 (Radius at P-H Intersection) The top-level performance requirement is that HPD_geom < 4 arcsec at a focal length of 10000.0 mm, with the revised focal-length tolerance: Configurations A and D (800-mm radius), +/- 2.4 mm; Configurations B and E (600-mm radius), +/- 3.0 mm; and Configurations C and F (500-mm radius), +/- 3.6 mm. Because multiple error terms (primarily relative-P-H-tilt and radius) contribute to the focal-length error, it is not necessary to sub-allocate errors in the Specification, provided the top-level requirement is satisfied. Consequently, we delete the requirement on the tolerance for the radius. The intent of the original tolerance on radius at the intersection plane was to be able to establish the axis of symmetry to within 10% of the 2-arcsec-radius circle into which at least half the flux must fall. In lieu of the tolerance on radius at the intersection plane, we add the following clarification on determination of the half-power diameter: The HPD_geom requirement means that, within the above-stated focal-length tolerance (and excluding diffractive scattering), at least half the flux must fall within a 4-arcsec-diameter circle centered on the axis of symmetry. The axis of symmetry shall be taken as that given by the prescription applied at +500 mm and at -500 mm from the intersection plane. That is, a 1000-mm-long optic, ideally replicated from the mandrel, with the forward parabolic end and aft hyperbolic end fixed at the positions described by the optical prescription, shall satisfy the HPD requirement for a 4-arcsec-diameter aperture centered on the axis defined by the prescription. Please note (Paragraph 1 of this Section) that we do not require the offeror to provide a precision alignment fixture to connect the separate P and H mandrels into a single mandrel. The stated minimum requirement is acceptable and perhaps even preferable. That is, we require the identification (including 3-dimensional coordinates) of reference surfaces and fiducial markings, sufficient to allow alignment of the separate P and H mandrels (or mirrors perfectly replicated from the mandrels) into an optic which would satisfy the focal-length (Section B.3.c.) and figure (Section B.3.f) requirements. Documents related to this procurement are available over the Internet and are in Microsoft Office 97 format and will reside on a World Wide Web (WWW) server, which may be accessed using a WWW browser application. The Internet site, or URL, for the NASA/MSFC Business Opportunities home page is http://nais.msfc.nasa.gov/cgi-bin/EPS/bizops.cgi?gr=CL&pin=62 Offerors are responsible for monitoring this site for the release of the solicitation and any amendments. Potential offerors are responsible for downloading their own copy of the solicitation and amendments (if any). [INSERT ANY APPLICABLE NOTES]

Web Link

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Record

Loren Data Corp. 20001221/ASOL006.HTM (D-354 SN5091W7)