To Do:

• Recreate stray light signal from 2018 flight in OpticStudio non-sequential model (Afaque and Trent)
• Design grating mask in SolidWorks
• Import/verify grating mask in OpticStudio
• Design SC1 glint baffle in SolidWorks
• Import/verify SC1 glint baffle in OpticStudio
• Confirm effectiveness of baffles in OpticStudio
• Send parts to ProtoLabs (or other) for quote on manufacturing
• etc.

Completed:

• Incorporated siderostat support into model
• Fixed FF2 aperture
• Incorporated gondola and nacelle into model
• Fixed scatter profiles and material types for various surfaces

To-Do's:

• Identify region on detector for stray light signal (hard rectangle at the bottom of the CCD)
• Trace light from stray light region out into the environment to determine potential viewports
• Analyze the potential viewports with and without the baffles

FIREBall-2 Straylight Analysis Notes

Advisor: Erika Hamden

Goal:

To complete thorough, accurate, and fruitful stray light analysis and reduction of the FIREBall-2 UV telescope.

Tasklist:

• Design detector baffle
• Re-design tongue baffle
• Re-design pupil plane baffle
• Design SC1 glint barrier
• Fabricate detector baffle
• Fabricate tongue baffle
• Fabricate pupil plane baffle
• Fabricate SC1 glint barrier
• Convert model into FRED
• Convert model into LightTools
• Check baffle performance in FRED
• Check baffle performance in LightTools
• Check baffle performance in OpticStudio
  etc.

Fig 1. Hard Shadow sans Shadow.

Fig 2. Hard Shadow plus Shadow.

Fig 3. Average of sans Shadow and plus Shadow.

Fig. 4 Difference of sans Shadow and plus Shadow.

Fig 5. Difference divided by Average.

EUREKA!

We finally have some agreement between the illumination patterns exhibited in the non-sequential optical model and the on-sky images from the 2018 flight campaign.

image000353.fits versus FIREBall-2_NSQ_2022_02_21_BalloonSneakPath_Cleanup.ZRD

Figure 1. At left, image000353.fits shows an example of stray light contamination from the 2018 flight campaign. At right, we present a detector viewer output demonstrating similarly structured illumination, produced by illumination of the back surface of FF2.

image000353.fits versus ...2022_03_09_UpdatedSneakPath.ZRD

Figure 2. By increasing the ray density, updating the source angular distribution to match the previously identified viewing angles onto the balloon (+/- 24 degrees from vertical), and including more interacting surfaces in the analysis, we find a fairly close agreement between the on-sky stray light distribution and the findings generated using the optical model. This is a big deal!

FIREBall-2 Regroup Meeting

April 9th, 2020

Erika Hamden, Afaque Khan, Trenton Brendel

Tasklist:

• Finish creating the FRED model (first priority)
• Send Bruno an email that asks directly where is the lens?
• SC1 Barrier

• Tell Affy how tall this barrier needs to be with rough dimensions, STEP file
• State where, relative to the SC1 mirror, it must be placed
• The barrier may be thicker, but it must accurately capture the rays

• Pupil Plane Baffle

• Must determine the positioning tolerances, beam size, location
• It may be that we have to design the pupil baffle for the two possible positions based on field lens positional deviation
• Will likely need to be very thin, because of positional tolerancing

• Must determine the exact position of the pupil plane baffle

• Design mechanism to hold it in place with the existing mechanical surfaces
• Much larger than the previous pupil plane baffle

• Grating Aperture Model (based on SEQ model)

• Want to make a mechanical interface to place aperture in the right spot

• Conical Baffle below FC1

• CAD model exists already, now need to check that it actually works
• Unsure as to whether the position of this baffle changes with the updates to the sequential model

• Field Stop/Tank Cap
• Detector Board Cover
  Afaque will make enclosing structure and check with Caltech re: cabling
• Tongue/FF2 Baffle
  Aeroglazed, @ Caltech
• Detector Baffle
  Aeroglazed, @ Caltech
• a
• b
• c

Notes:

• Clipping of the beam by the baffles
• Poor raytrace efficiency in OpticStudio
• Scattered light model
• Discrepancies between CAD model and OpticStudio model (both NSC and SEQ)
• Can't measure the positioning of the field lens
• Must deduce one reference for everything so that

Completed:

• Procured University Gratis License from Photon Engineering
• Provided stray light update to FIREBall-2 team during morning telecom
• Soften trace requirements to increase likelihood of finishing ray trace (OpticStudio crashing indefinitely)
• Obtain Polaris-M License

To-Do's:

• Import OpticStudio model into FRED
• Test trace on FRED to confirm import success
• Talk to Dr. Koshel about ongoing stray light analysis and ask for advice and tips (esp. FRED help)
• Continue fine tuning trace parameters to ensure trace success