GMAGAO-X R-03 Telescope jitter environment

[dmkelly42]

Risk creation date: 9/13/2022

Last Modified: 10/4/2022

Risk type: Technical

Risk Approach: Mitigate

Risk Owner: Doug Kelly

Risk Statement:

If the GMT does not control mechanical vibrations, GMagAO-X will not be able to control jitter to the target of 0.3 mas (0.05 lambda/D at 800nm).

Risk Effects:

If GMagAO-X does not control jitter to 0.05 lambda/D, it will not be able to achieve the coronagraphic contrast required to meet its primary science goal of measuring reflected light from Earth-like planets around nearby, Sun-like stars.

Risk Assessment:

Risk Ratings	Likelihood	Consequence
Initial	4-likely	4-high
Current	4-likely	4-high
Target	2-unlikely	3-moderate

Initial Risk Notes:

Construction of the GMT will not be completed for 10 years so the vibration environment cannot be measured. We will convey our needs to the GMT and will provide ideas and encouragement for the development of vibration-reducing measures.
Contrast depends on tip-tilt to the 4th power so good jitter control is essential.
Our current, cantilevered M3 design leaves us susceptible to observatory vibrations.
We will be photon-limited when it comes to measuring jitter on many targets (>8.5mag).
The minimum useful stability is 4 lambda/D. At that level of jitter, the 7 telescope mirrors would not be phased to each other, so the observatory would perform like 7 separate 8-m telescopes. GMagAO-X would still be valuable because of its small inner working angle.

Cost Impacts:

Estimated cost if risk is realized:
TBD

Explanation for cost risk:

Risk mitigation list:

• 1. Perform modeling to predict the GMT jitter environment
• 2. Discuss ideas for jitter measurement and control with the GMT (accelerometers; lasers)
• 3. Discuss jitter measurement and control with the TMT and EMT projects.
• Design GMagAO-X to reduce its jitter susceptibility (R-03 mitigation) #12
• 5. Perform analysis to determine the signal level required to meet the GMagAO-X jitter requirement. From this, determine the required integration time vs source brightness.