nic scott

Telescope Systems Scientist

Status of CHARA telescopes

The CHARA Science Meeting 2026 - Soccoro

Where does CHARA have single point failures....

i.e. where the nightmares lie? 

  • aging equipment
  • time sinks
  • lack of spares
  • discontinued components
  • supply chains becoming questionable
  • other risks

still....but slightly less so

  • Mirror recoats - W2, E2 ​
  • New drives - S2EL, W1EL, E1EL, S1AZ
  • New cylinder control
  • New AOB & TEMA - soon at S2
  • PI actuators & TT piezos, cal source and other motors - will need future replacement/upgrades
  • CHARIOT
  • Future​​

Mirror recoats

scope date last done tbd
S1 4-2022 2026
S2 8-2021 2026
W1 2-2025 2027
W2 1-2026 2028
E1 12-2024 2027
E2 1-2026 2028
  • TelAO WFS for fine alignment
  • camera for alignment scope speeds and improves EL axis alignment
  • sourcing small mirror coating chamber

cylinder upgrade

Drive Upgrade - S2EL, W1EL, E1EL, S1AZ

  • Existing drives are ~25 years old & discontinued

  • 12 drives and motors (plus spare) in hand from Parker

  • Drive assemblies fabrication done, only needs SPA mod

  • Spare Dojen

  • Install during daytime during semester, but some night hrs needed for software and tuning

  • Should be able to finish by end of next winter shutdown

  • move to pulse mode + RPi+custom hat pulse generator

  • E1EL bearing replaced - made spares

current:

  • single motor driver (r256)
  • multiplexed relays
  • daisy chained
  • sequential operation only
  • little or no feedback, timing-based
  • very difficult to diagnose/repair
  • not necc. interchangable

ideal (Noy's talk):

  • 1 drive per axis
  • no multiplexing
  • parallel operation
  • expensive (>$10k/scope)
  • <$3k

Tiptilt, PZT issues, actuators, hexapods?

hexapod/piezo tiptilt system 

  • needs to function hanging upside down
  • ~$40-50k each

  • TT PZT & actuator concerns

  • PI P-855.20 PZT's discontinued in 2018 - no working spares

  • can use DM for TT but no on-sky reconstructor

  • could replace with Thorlabs PZT's or PI actuators+PZT

  • PI M-224.20 actuators discontinued in 1992 - 1 spare

CHARIOT

K=5.2 so far, new pickoff,

new pc, CREDOne,

new output optics, dichroics,

FT w/ MIRCX, moving to 4 beam

sub-1% diameter precision for K<=2

"Towards quantum-enhanced long-baseline optical/near-IR interferometry"

Rajagopal et al. (2024)

Initial HBT experiments with BNL

CHARA Array Future Plan (2025 meeting)

Outline:

  • Phase 0: AC at telescopes
  • Phase 0.1: new IR dichroics for beam samplers
    • Improve multi-wavelength performance
    • Wider bandwidth for better STST performance
      • CRED1, bluer for science, WFS on a single chip?
    • Dual-star phase reference mode
  • Phase 0.5: upgrades of telAO
    • Redesign M2, go to focal design?
  • Phase 1: central 2m + AO + OPLE upgrades
    • LabWFS control new telDM,
    • Longer delay + better metrology or double-decker carts
      • Visible-sensitivity, resolution, stability →  needed for nulling 
  • Phase 2: replace 1m's with 2m's
    • Propagate upgrades from central 2m
  • Phase 3: full CMA - outer km baseline fiber array

Outreach - Shadow the Scientists, Universe Today w/ Fraser Cain, All Science Considered (upcoming)

RIP "Winky"