NIRCam ETU Testing at LMATC, Palo Alto Kailash C. Sahu

What’s NIRCam? NIRCam is the near-infrared camera (0.6-5 microns) for JWST –Dichroic used to split range into short (  m) and long (2.4-5  ) sections –Nyquist sampling at 2 and 4  m –Coronagraphic capability for both short and long wavelengths –Low-resolution spectroscopic capability in the LW channel. NIRCam is the wavefront sensor –Must be fully redundant

2 Channels Per Module Each module has two channels (0.6 to 2.3  m and 2.4 to 5  m) –7 wide band filters (4 SW, 3 LW) for deep surveys –Survey efficiency is increased by observing the same field at long and short wavelength simultaneously Pixel scale: SW: 0.032”/pix LW: 0.064”/pix Long wavelength channelShort wavelength channel Module A Module B 2.2’

Focus and alignment mechanism Coronagraph occulting masks First fold mirror Collimator lens group Dichroic beamsplitter Long wave filter wheel assembly Long wave camera lens group Long wave focal plane housing Short wave filter wheel assembly Short wave camera lens group Short wave fold mirror Pupil imaging lens assembly Short wave focal plane housing Light from OTE Pick-off Mirror Module A

NIRCam ETU/WFS Testing 1-9 April at LMATC (Lockheed Martin Advanced Techonology Center), Palo Alto First ~3 days (after the “Red Chamber” attained operating temperature of ~38K) spent on SCA/Assembly testing, rest on WFS testing (only with the SW channel). People from STScI: Massimo Robberto, Elizabeth Barker, Kailash Sahu (WIT). George Hartig, Erin Elliot (TEL)

NIRCam ETU/WFS Testing Tests were generally very successful – Operated with the flight software over eight days with no crashes or major problems – Wavefront sensing components were demonstrated to work in the NIRCam pupil Main problems: - Transfer of FITS files often needed manual intervention. - PIL (Pupil Imaging Lens) had some alignment problems. “First Light” Fuzzy because of chamber vibrations, tests were done with “pulsed light” Structure in this image is due to the known poor alignment of the OMA and ETU at this early stage.

Weak Lens Images The shapes are very close to predicted images. Ghosts are due to reflections in the OMA optics, not NIRCam

DHS Spectra Spectra are at the correct angle. Known emission line in the super continuum source being used for illumination. A spectrum extracted from the previous image. The “notches” in the filter used in series with the DHS are apparent.

Flat Fields from Internal Red Chamber Lamps

Detector Linearity from Chamber Lamp Data Sample ramps from independent exposures Black: Without linearity correction Blue: After linearity correction These data are the first chance we had to check linearity with ASIC + SCA. Overall linearity is good (better than 5%) and is dominated by SCA, not ASIC. Some systematic effects at “low” count rates need to be investigated further.

(a)Over-saturated point source image taken during ETU testing. Estimated counts (from the ghost): 650,000 to 1 million DN. (b) Exposure taken immediately after (a). Counts at the peak of the point source: ~650 DN (< 0.1%) (c) Exposure taken ~4 minutes later. Peak counts: ~80 DN. Detector Latency (a)(b) (c)

SUMMARY Initial SCA and WFS testing results are very encouraging. The software operated relatively smoothly, but problems were identified which will be rectified in time for FM testing. Participations from all the groups (GSFC, LMATC, UA and STScI) were coherent and complimentary. All the ETU Test data are being archived at STScI through SID archive.

Sample Images from the Focus Sweeps These are not organized in any fashion and some were taken at different wavelengths.

PIL Image of DHS Blue areas are due to the missing pieces in the DHS. Segment gaps and the secondary supports are evident.