SPECIFICATIONS.pdf

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National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

LISA-GSE-SPEC-0001

LISA Telescope Wavefront Verification

Interferometer (WaVI) Specification

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LISA Telescope Wavefront Verification Interferometer (WaVI) Specification LISA-GSE-SPEC-xxxx Revision (-) ii

Preface This document is under control by the LISA project configuration control board (CCB).

Changes to this document require prior approval of the LISA CCB chairperson or designee.

Proposed changes shall be submitted in the LISA Technical Data Management System (TDMS) via a configuration change request (CCR) along with supportive material justifying the proposed change. Changes to this document will be made by complete revision.

All of the requirements in this document assume the use of the word "shall" unless otherwise stated.

Table of Contents

1 INTRODUCTION

1.1 Overview

1.2 Scope

1.3 Related Documentation

1.3.1 Applicable Documents

2 REQUIREMENTS

2.1 Interferometer Requirements

2.2 Electrical

2.2.1 Camera

2.2.2 General

2.3 Physical, Thermal, Mechanical

2.4 Thermal Environment

2.5 Software

2.6 Design and Construction

2.7 Logistics

3 PREPARATION FOR DELIVERY

1 INTRODUCTION

1.1 Overview

One of NASA’s contributions to the LISA partnership with ESA is to supply the precision telescopes that transmit and receive the 1.064 micron coherent laser light. These telescopes can be considered a hybrid laser communications and interferometer beam expander. Similar to a laser communication system, the transmit and receive transmissions are linearly polarized allowing the telescope to communicate simultaneously with the detection system in the other spacecraft. But unlike a laser communications system, the telescopes are part of a very large sub-fringe counting system that measures very small distortions on the level of a few picometers along the optical path. Therefore, changes in the telescope wavefront will have a significant impact on the sensitivity of the system and the ultimate success of the mission. The telescope stability required for LISA is a few picometers/√Hz in all parameters that impact the optical path length in the frequency band from 0.1 mHz to 0.1 Hz, and is a few nanometers to micrometers for time durations which vary from hours up to even a year. The long-term telescope stability is a key factor in the success of the LISA mission.

This specification lists the requirements currently deemed necessary for an interferometer that will be used as Ground Support Equipment (GSE) to verify the optical performance of the telescopes.

1.2 Scope

This specification establishes the performance, functional and interface requirements for the GSE interferometer.

1.3 Related Documentation

1.3.1 Applicable Documents

The following documents, of the exact revision shown, form a part of this specification to the extent specified herein. In the event of conflict between documents referenced and the detailed contents of this specification, the requirements specified herein shall govern

NASA GSFC Documents:

Document No. Document Title LISA-GSE-SOW-0001 LISA Telescope Wavefront Verification Interferometer (WaVI) SOW

2 REQUIREMENTS

2.1 Interferometer Requirements

INT-10 Wavelength: The nominal operating wavelength shall be 1064.5+/-1 nm INT-30 Instrument wavefront quality: The wavefront quality ≤ 1/15 wave P-V over the clear aperture, excluding piston, tip, and tilt INT-35 Instrument sample beam optical power: The sample beam should have ≤ 1/20 wave optical power, P-V over the clear aperture, excluding piston, tip, tilt, and residual higher-order aberrations INT-40 Reference path: The reference path shall have ≤ 1/15 wave P-V wavefront error excluding piston, tip, and tilt over the clear aperture INT-50 Polarization: Linear or circular INT-60 Aperture diameter: The instrument clear aperture shall be in the range ≥ 6 mm and ≤ 10 mm INT-70 Aperture illumination uniformity: There shall be < 20% P-V variation over the center 3 mm and < 50% variation over the full clear aperture INT-80 Coherence length: The coherence length shall be > 20 meters INT-90 Optical Zoom: None preferred or required.

INT-100 Sample beam entrance pupil: The entrance pupil of the returning sample beam should be external to the interferometer and should be at least 45 mm minimum distance from the last physical extent of the interferometer in the direction of the sample beam leaving the instrument.

INT-105 Entrance pupil focus adjustment: The entrance pupil should have focus adjustment range of at least 25 mm in real space outside the instrument.

INT-110 Phase acquisition time registration: All phases required for the measurement shall be taken simultaneously.

INT-115 The minimum exposure time shall be ≤ 0.1 msec for all needed phases.

INT-120 Frame rate: The frame rate shall be ≥ 5/sec. Note: Frame rate is defined here to be the minimum rate at which all needed phases can be acquired and stored in (RAM) memory.

INT-130 Laser power: The laser power shall be ≤ 600 mW (at the laser itself) INT-140 Laser power stability: The laser power stability shall have < 12 mW P-V after warm-up.

INT-150 3σ repeatability: The 3 sigma repeatability shall be <0.0035 λ RMS.

Note: Methodology for testing this specification will be via a mutually-agreed-upon method in an environment of 20±1°C & 40±10% RH.

2.2 Electrical

2.2.1 Camera

INT-200 Focal plane: ≥ 1000 x 1000 pixels INT-210 Quantization: ≥ 12 bit ADC

2.2.2 General

INT-220 AC voltage: 110V/60 Hz single phase with ground INT-230 AC current: ≤ 15 amps total, including surge

INT-240 Signal and power connectors: The electrical connectors shall be of a standard type used for a cleanroom environment INT-250 Laser On indicator warning: There shall be a laser on indicator that is a bright light, which is clearly visible and labeled INT-260 Laser aperture/beam block indicator: There shall be an interferometer aperture output indicator that is a bright light which is clearly visible from a direction other than that which the beam exits the interferometer and is labeled Note: This light is to be a different color than the Laser On indicator of INT-250

2.3 Physical, Thermal, Mechanical

INT-300 Interferometer (head) dissipation: ≤ 5 W (fiber-coupled laser sources preferred with minimum 1 meter cable length) INT-310 Air turbulence: There shall be no air-turbulence-creating components in interferometer head (fans, etc.)

Note: With NASA prior approval, the system can have a light path separated from turbulence via baffles.

INT-320 Power supply: The power supply shall be remote from the interferometer optical head INT-330 Power supply cable length: The remote power supply shall be > 1 meter from the interferometer head INT-350 Mounting: The interferometer head shall be mountable to a standard optical bench (compatible with ASE ¼-20 screws on 1” centers) Note: all other components can be rack or bench-top mounted

2.4 Environment

INT-400 Survival: The interferometer shall survive and be fully function after exposure to a temperature range from -1° to 38° C in a non-condensing environment.

INT-410 Operating: The interferometer shall meet all optical specifications in a temperature environment of 20 +5/-3 °C, Relative humidity 10-70%.

2.5 Software

2.5.0 Platform

INT-500.5 The computer platform for this instrument shall be based on a current operating system that is supported by the vendor and the US Government. (e.g. Software platforms such as Windows 7 or XP are excluded.) The platform should be capable of being networked and have provisions for a “modern” data interface such as USB and capable of being connected to an external hard drive for back-up, while connected to a network.

2.5.1 Interferometer Acquisition and Control

INT-500 Display rate: The refresh rate shall be ≥ 1 display/sec for data being displayed.

INT-505 Detector integration control: The integration time should be controllable from the minimum (per INT-110) to > 500 milliseconds to accommodate varying light levels INT-510 Saturation indication: The software shall clearly flag saturated pixels on the display screen

2.5.2 Data Handling

INT-520 Data handling: The software system shall be capable of handling and storing all processed data at the maximum frame rate or better. Note: This assumes a computer with memory adequate to the data set. That is, the software should not limit the data acquisition rate.

INT-525 Raw data (per phase): The software system shall be capable of acquiring and storing all phases of raw data at the maximum frame rate or better. Note: Under the same assumptions as INT-520.

INT-530 Time tagging. The software system shall be capable storing a time stamp for the start of a measurement sequence and preferably each saved measurement.

INT-550 Bad pixel mapping/correction: The software system shall be capable of mapping and correcting bad camera pixels as part of the frame processing. Note: This could be from the camera manufacturer but should be included in the manual or some data/calibration package provided with the instrument.

INT-555 Calibration files: The software system shall be capable of generating and saving time-stamped calibration files. These will be for two cases 1. Individual phase-level (for stray light, illumination variation, and internal distortion, as applicable); 2. Unwrapped phase-level (for interferometer WFE back-out, cavity error, cavity distortion, etc. as applicable).

INT-560 Calibration file subtraction: The software system shall be capable of using the calibration files for subtraction from processed data (wavefront only).

INT-570 File import and export formats: The software system shall be capable of importing and exporting, at a minimum, ASCII TXT, CSV, and Code V *.INT (phase map and Zernike) files.

2.6 Design and Construction

INT-600 All components and subsystems shall be made of compatible material that are suitable for a Class 10,000 or better environment. Laser head components, Class 1000.

INT-610 All components and subsystems shall be cleaned and in compliance with use in a Class 10,000 or better environment.

INT-620 Laser head components and subsystems shall not outgas condensable molecular contaminants (siloxanes, etc.) per SEMI Standard F21-85 & SEMI-E108-0301 and updates/supplements.

INT-630 Laser Class markings shall be on the remote laser housing (compliant with FDA

21CFR1040.10)

INT-650 All electrical components, wiring and circuits shall be NFPA 70, National Electrical Code compliant.

INT-660 All separate assemblies weighing more than 10 pounds shall have appropriate handling points and, if appropriate, handles or lifting eyes.

2.7 Logistics

INT-700 The transportation and delivery shall be consistent with shipping contamination-sensitive optical hardware.

3 PREPARATION FOR DELIVERY

INT-800 The shipping container and/or method must ensure the cleanliness (including molecular) and the protection (environment compatible with INT-400, shock, vibration, electrostatic discharge, etc.) that is necessary for this type of sensitive, clean room optical equipment.

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3 preparation for Delivery