mendillo 2019 spie poster - umass lowell | umass lowell 2019 spie poster... · hodm probe patterns...

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Decoupling the image-plane and low-order wavefront sensors for the PICTURE-C coronagraph Christopher Mendillo1, Kuravi Hewawasam1, Glenn A. Howe1, Jason Martel1, Timothy Cook1, Supriya Chakrabarti1 1: UML

Abstract: The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) mission will directly image debris disks and exozodiacal dust around nearby stars from a high-altitude balloon using a vector vortex coronagraph. PICTURE-C employs both image-plane wavefront sensing for high-order wavefront control and a reflective Lyot-stop sensor for low-order wavefront control. Since both of these systems lie downstream from the coronagraph's deformable mirror, and since both must run simultaneously, they must be calibrated as to not interfere with each other. The deformable mirror probe patterns required for image-plane sensing appear as wavefront errors to the low-order sensor. This paper presents simulations of low and high-order wavefront sensing for PICTURE-C and calibration techniques for decoupling the two sensors.

Funded by NASA grant: NNX15AG23G

LLOWFS influence images for LODM Zernikes

HODM probe patterns for HOWFS

LLOWFS influence images for HODM probes

LLOWFS Zernike measurement of each HOWFS DM probe pattern

The Zernike on the X-axis is commanded on the LODM with a 10nm RMS amplitude. The dots show the RSS of all LLOWFS-measured Zernikes other than the commanded one.

Each dot represents one of the 8 HOWFS probe patterns. Red is uncalibrated. Black is calibrated.

Single-point calibration: Multi-point calibration:HOWFS & LOWFS cross-coupling:Use unique reference image for each HODM probe Use unique Zernike matrix for each HODM probeHODM probe patterns register as Zernikes on LLOWFS

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M1

Avionics

Star Tracker

Trim Weights

CoronagraphM2

ElectronicsWASP Hubs

POWER SUPPLY

LODM CTRL

HEX CTRL

CPUTEMP

TM

SS

HEX

CCD

POL2

POL1

OAP4

HODM 952ch

OAP2

OAP1 Dichroic pass < 540nm

M3

Acquisition Camera

VVC

Lyot Stop

24” x 48” Carbon Fiber Bench

SH LOWFS

Lyot LOWFS

CCD

From Telescope

LODM 97ch

OAP3

PICTURE-C Coronagraph

BP Filter

CCD

5 Color Science Camera