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 - to be installed soon at S2
• PI actuators & TT piezos, cal source and other Ametek-Haydon-Kerk-Pittman motors - will need future replacement/upgrades
• CHARIOT
• Future
  • ​​AC, replace all AOB/TEMA/Crypt controlers, new cable puller, new spycams
    • hexapods

Mirror recoats

• TelAO WFS for fine alignment
• camera for alignment scope speeds and improves EL axis alignment

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 obtained

• 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

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 M-227.25 actuators+PZT

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

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

Rajagopal et al. (2024)

Initial HBT experiments with BNL

Plan 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, All Science Considered (upcoming)

RIP "Winky"

(?-2025)