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Status of JWST/ISIM Test Program. Scott Friedman TIPS/JIM April 18, 2013. Acknowledgments. Thanks to the following people for providing much of the information used in this presentation Randy Kimble (GSFC) Doug McGuffey (GSFC) Joe Sullivan (Ball)

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Status of JWST/ISIM Test Program

Scott Friedman


April 18, 2013



Thanks to the following people for providing much of the information used in this presentation

Randy Kimble (GSFC)

Doug McGuffey (GSFC)

Joe Sullivan (Ball)

George Hartig (STScI), for many useful discussions



ISIM = Integrated Science Instrument Module (1)

OTE = Optical Telescope Element (2)

(analogous to the HST OTA)

OSIM = Optical Telescope Element Simulator (3)

(the light source for ISIM testing)



OTE Simulator (OSIM)

  • Full field cryogenic optical simulator of JWST OTE.
  • Schmidt system with no corrector plate
    • Only a single powered optic – spherical primary mirror
  • Provides point source illumination over 0.642 – 5.6mm
    • Point sources can be steered to any SI field point
      • Pupil must translate to hold exit pupil fixed
    • Some extended source capability using a diffuser
  • Beam Image Analyzer (BIA) measures quality of OSIM sources
    • Uses Phase Retrieval (PhaRet) camera (using a NIRCam H2RG detector) and Point Diffraction Interferometer for redundancy
  • Provides the only images in entire JWST ground test program that will look like those in orbit

OSIM Cryo-Vac Tests

First OSIM cryo-vac test completed summer 2012. Partially successful

Optical results were stable and good. Jitter and stray light appear within requirements. Thermal performance nominal.

BIA V1 stage froze at cryo temperatures.

Facilities issues troublesome (power outages, N2 leaks).

Second OSIM cryo-vac test dates

pumpdown March 15

data taking started April 14

completion May 26

It is critically important to validate OSIM so its performance is not in question when ISIM testing begins.


OSIM Test Configuration – Real Life

OSIM in the 100K section (bottom)

Beam Image Analyzer in the 30K section (top)


Original ISIM Test Plan

All science instruments delivered to GSFC fully calibrated and qualified.

SIs integrated into the ISIM structure mechanically, electrically, and thermally (flight-like to the extent possible).


Verify focus, pupil alignment, image quality, etc.

Verify thermal performance.

Verify wavefront measuring capabilities of SIs (especially NIRCam).

Test Operations Script Subsystem (OSS) and event driven ops.


Original ISIM Test Plan (continued)

Environmental test series

Vibration, acoustic, gravity release, EMI/EMC.

Cryo-Vac 2

Similar to CV1 but not everything repeated.

Deliver to JSC for OTE+ISIM testing


But Plans Change…

Instruments not available for CV1

  • NIRCam – will be delivered to GSFC in May
  • NIRSpec – will be delivered to GSFC in September

Many hardware items not available for CV1, most importantly new near-IR detectors.

We could wait for these to arrive but that would defer a lot of risk. So…

A new cryo-vac cycle has been added to the beginning, a cryo-vac Risk Reductioncampaign: CV1 RR


Three ISIM Cryo-Vac Campaigns

Cryo-Vac 1 RR

  • Science instruments: MIRI and FGS/NIRISS only.
  • CV1 RR goals include:
    • Validation of OSIM as light source for CV campaigns
    • Confirm MIRI and FGS/NIRISS operate in ISIM configuration
    • Confirm thermal models of ISIM environment
      • Hardware well-instrumented to measure this
    • Measure stray light backgrounds especially in MIRI and FGS
    • Assess jitter properties of ISIM. Will pulsed sources or vibration isolators be required?
    • OSS scripts, including “Day in the life” test.

Three ISIM Cryo-Vac Campaigns

Cryo-Vac 1 RR Instrument Verification

NIRISS performance characterization

Some modes have not been tested end-to-end in the instrument

MIRI regression testing

Apply NRB noise mitigation recommendations to flight system

MIRI MRS spatial resolution measurement

PSF during FM testing was compromised

Tune-up of FGS ASIC

This must be done for 13 detector/ASIC pairs in CV3.

Initial trending of MIRI and FGS/NIRISS

CV1 RR is designed to retire risk and increase the chances that CV2 and CV3 execute smoothly


Three ISIM Cryo-Vac Campaigns

Cryo-Vac 2

  • Performance verification campaign
  • All 4 flight instruments present
    • but not all flight hardware…
  • Optical metrology and alignment with fully populated ISIM structure
  • Establish first trending data for NIRCam and NIRSpec
    • Continue trending for MIRI and FGS/NIRISS

After Cryo-Vac 2 install all remaining hardware and then perform the environmental test series

  • vibration, acoustic, gravity release, EMI/EMC

Three ISIM Cryo-Vac Campaigns

Cryo-Vac 3

The campaign to establish that ISIM meets all requirements

  • Contains all flight hardware elements
  • New hardware (hold on to your hats…):
    • All new near IR detectors (15 total)
      • Have to get metrology right the first time. There will be no CV 4!
    • New NIRSpec Micro-Shutter Assembly (MSA)
    • MIRI Heat Exchanger Stage Assembly (HSA)
    • New NIRISS filter wheel and pupil wheel motors
    • New NIRISS GR700XD grating (possibly)
    • New MIRI flight electronics boards (possibly)

ISIM Cryo-Vac Schedule

Cryo-Vac 1: 8/9/13 – 10/12/13 65 days

Cryo-Vac 2: 5/23/14 – 9/9/14 109 days

Cryo-Vac 3: 6/4/15 – 8/17/15 74 days

35 weeks of 24/7 operation will require a lot of planning and support from all stakeholders.


What’s Next?

OTIS Testing

Let’s review equation (4)


This is a lot of hardware but not the whole observatory! In particular, the spacecraft is not present during OTIS testing.


OTIS Test Schedule*

  • OGSE-1: Jan – Feb 2015
  • OGSE-2: May – Jun 2015
  • PF thermal: Jan – Mar 2016
  • OTIS test: 2016 – 2017

Recall that ISIM CV3 is scheduled for Jun – Aug 2015. Possible collision for some people supporting both tests.

* these dates highly uncertain (at least to me)



  • We have a series of challenging test campaigns ahead that are just beginning
  • They get progressively more complex which provides the opportunity to learn in stages and to recover from problems
  • The schedule is holding, but margin is being used. Not much room for expansion of effort. But ISIM and JWST project hold months in reserve.
  • Very important for the flight hardware to be delivered in a timely fashion so CV3 can go forward as planned.
  • This is our future. Let’s make it happen!