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REVIEW 2 major objections 16 references

Rubin M1M3 Dynamic performance : stability and actuation during operations

T0 review · 2 major / 0 minor · reviewed 2026-07-02 · grok-4.3

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Pith's one-line read Dynamic tests at 20 percent speed confirm the M1M3 mirror stabilizes within five seconds after slews.

desk verdict This is a routine engineering commissioning report on Rubin M1M3 tests that documents necessary validation work but rests its readiness claim on an untested extrapolation from 20% speed runs. read the letter →

arxiv 2607.00163 v1 pith:DCDY3I46 submitted 2026-06-30 astro-ph.IM

HyeYun Park , Petr Kubánek , Kshitija Kelkar , Ignacio Sevilla-Noarbe , Andrea Jeremie , Brian Stalder , Bruno C. Quint , David Sanmartim
show 15 more authors
Dominique Boutigny Douglas R. Neill Erik Dennihy Felipe Daruich Freddy Muñoz Arancibia Kevin Fanning Kevin Reil Laura Toribio San Cipriano Malhar Sonaniskar Marina S. Pavlovic Noah Gonzalez Paulina Venegas Sandrine Thomas Tiago Ribeiro Yijung Kang
This is my paper
classification astro-ph.IM
keywords M1M3mirrordynamictestspneumaticactuatorsslewandsettletelescopestabilityRubinObservatorycellsupport
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper reports results from a series of dynamical tests on the 8.4 m, 53 ton M1M3 mirror system installed in the Simonyi Survey Telescope. These tests measure how the system, supported by 156 pneumatic force actuators and six hardpoint actuators, responds to slew motions, gravity changes, and external loads while maintaining stability and settling vibrations quickly. The central effort is to check whether the mirror can meet the motion and settling requirements for the Legacy Survey of Space and Time. A sympathetic reader would care because the ability to move rapidly between fields and begin clean exposures directly determines how much sky the survey can cover in a given night.

What carries the argument

The 156 pneumatic force actuators combined with six hardpoint actuators that dynamically adjust to counteract gravitational and inertial loads during telescope motion.

What would settle it

A full-speed slew at any elevation where the mirror fails to damp vibrations to the required level within five seconds or shows actuator force instability.

Watch

Extended reading notes

Core claim

The M1M3 mirror system, controlled by 156 pneumatic force actuators and six hardpoint actuators, meets the requirements for safety, stability, and image quality under realistic operating conditions, as shown by tests that evaluate slew-and-settle behavior, elevation balancing, force response, and earthquake response across the operational envelope of velocities and accelerations.

Load-bearing premise

Tests conducted at 20 percent of operational speed are enough to guarantee performance at full nominal speeds and 50 percent higher across all elevations and under earthquake loads.

Editorial extensions

If this is right

  • The M1M3 subsystem is ready for routine survey operations.
  • Lookup tables for elevation balancing can be used without further major revision.
  • The pneumatic actuator system maintains stability across tested attitudes including earthquake response.
  • The collected data can be used directly to refine performance models.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If full-speed tests reproduce the same settling times, the telescope can move to integrated survey operations without redesign of the actuator control.
  • The demonstrated settling performance sets a practical limit on how quickly the survey can cycle between pointings.
  • The same actuator compensation approach may apply to other large mirrors that must track changing gravity vectors during fast slews.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 0 minor

Summary. The manuscript reports results from a series of dynamic tests on the 8.4 m, 53-ton M1M3 primary/tertiary mirror system of the Vera C. Rubin Observatory Simonyi Survey Telescope. Using 156 pneumatic force actuators and six hardpoint actuators, the tests evaluate slew-and-settle behavior, elevation-axis balancing, lookup-table updates, force response and stability across telescope attitudes, and earthquake response. The central claim is that these tests, described as spanning the operational envelope of slew velocities and accelerations, demonstrate the M1M3 subsystem's readiness for routine survey operations and supply validation data for performance modeling.

Significance. If the quantitative test outcomes confirm that the system meets the 5-second post-slew settling requirement and maintains stability under gravitational and inertial loads, the work would provide important empirical validation for a key subsystem of a major survey telescope. Such data are directly relevant to operational planning and ongoing modeling for the Legacy Survey of Space and Time.

major comments (2)
  1. [Abstract] Abstract: The assertion that the tests 'span the operational envelope of slew velocities and accelerations' while being performed 'at just 20 % of its operational speed' is internally inconsistent without further justification. Inertial forces and vibration excitation scale with velocity squared; therefore, results obtained at 20 % speed cannot be assumed to demonstrate compliance at nominal or 1.5 imes nominal speeds (including earthquake loads) unless a scaling analysis or additional full-speed data are supplied.
  2. [Abstract] Abstract: No quantitative metrics—settling times with uncertainties, peak displacements, actuator force residuals, or pass/fail criteria—are reported to support the readiness conclusion. The central claim that the subsystem is ready for routine operations therefore rests on an unquantified assertion rather than on presented evidence.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review. The comments highlight important issues with the abstract that we will address through revision. We respond to each major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The assertion that the tests 'span the operational envelope of slew velocities and accelerations' while being performed 'at just 20 % of its operational speed' is internally inconsistent without further justification. Inertial forces and vibration excitation scale with velocity squared; therefore, results obtained at 20 % speed cannot be assumed to demonstrate compliance at nominal or 1.5 times nominal speeds (including earthquake loads) unless a scaling analysis or additional full-speed data are supplied.

    Authors: We agree the abstract wording is inconsistent and requires clarification. The tests were performed at up to 20% of nominal speed during the integration phase, with the phrase 'operational envelope' intended to describe the range of attitudes and achievable velocities at that stage rather than full nominal speeds. We will revise the abstract to explicitly state the tested velocity range (up to 20% nominal) and remove any implication of full operational speeds. The manuscript does not contain a scaling analysis for v-squared inertial effects or full-speed data, as such tests are planned post-integration; we will add a brief note acknowledging this limitation and its implications for earthquake response extrapolation. revision: yes

  2. Referee: [Abstract] Abstract: No quantitative metrics—settling times with uncertainties, peak displacements, actuator force residuals, or pass/fail criteria—are reported to support the readiness conclusion. The central claim that the subsystem is ready for routine operations therefore rests on an unquantified assertion rather than on presented evidence.

    Authors: We acknowledge that the abstract presents only a qualitative summary and does not include specific quantitative metrics. The body of the manuscript contains the supporting data and figures on settling behavior, displacements, and forces. To address the concern, we will revise the abstract to incorporate key quantitative results drawn from the manuscript, including settling times relative to the 5-second requirement, representative peak displacements, actuator force residuals, and the pass/fail criteria applied. revision: yes

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity; purely empirical test results with no derivation chain

full rationale

The paper reports outcomes from a series of physical dynamic tests on the M1M3 mirror system, including slew-and-settle behavior, actuator force response, and stability across attitudes. No equations, first-principles derivations, fitted parameters, or model predictions are presented that could reduce to their own inputs. The readiness claim rests directly on measured settling times, force adjustments, and vibration damping within the tested conditions, without any self-citation load-bearing steps or ansatz smuggling. This is a standard empirical validation report whose central content is independent of any internal reduction.

Assumptions & free parameters 0 free parameters · 0 assumptions · 0 invented entities

No mathematical model, free parameters, or invented physical entities are present; the claim rests entirely on the interpretation of empirical test data described at summary level in the abstract.

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Cite this review

Pith. "Pith review of Rubin M1M3 Dynamic performance : stability and actuation during operations." pith.science (2026). https://pith.science/paper/DCDY3I46

@misc{pith2026260700163,
  author       = {Pith},
  title        = {Pith review of: Rubin M1M3 Dynamic performance : stability and actuation during operations},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/DCDY3I46}},
  note         = {Machine review of arXiv:2607.00163}
}
read the original abstract

The Vera C. Rubin Observatory is preparing to commence the Legacy Survey of Space and Time with the fully integrated Simonyi Survey Telescope. To verify that the primary/tertiary (M1M3) mirror system is ready to meet the demanding survey requirements, dynamic tests of the 8.4 m, 53 ton M1M3 system were conducted to assess safety, stability, and image quality under realistic operating conditions. The M1M3 is supported by 156 pneumatic force actuators and positioned, relative to its mirror cell, by six hardpoint actuators that together must counteract gravitational and inertial loads during rapid telescope motion. The Rubin Observatory telescope mount is capable of moving at a rate that meets its nominal motion requirements, and can approach it maximum allowable values that are 50 percent higher. Even at just 20 % of its operational speed, it is an exceptionally fast motion for such a large structure. After slewing, the system must stabilize and dampen vibrations within 5 seconds to ensure image quality during observations. Achieving this rapid settling requires precise control of 156 force actuators, which must adjust dynamically with changes in telescope elevation to compensate for gravity effects. We present results for M1M3 from a comprehensive series of TMA dynamical tests spanning the operational envelope of slew velocities and accelerations. The analysis evaluates elevation axis balancing and lookup table updating as we install the M1M3 mirror; slew-and-settle behavior, force response and stability of the pneumatic actuator system across telescope attitudes including responses to the earthquake. The results demonstrate the readiness of the M1M3 subsystem for routine survey operations and provide validation data for ongoing performance modeling.

Figures

Figures reproduced from arXiv: 2607.00163 by the authors.

Figure 1
Figure 1. M1M3 insgtallation. RubinObs/NOIRLab/SLAC/NSF/DOE/AU. [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. M1M3 balance forces - surface error plots [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. M1M3 settle time in axes xyz for a standard LSST survey like day of observations, shown against the 1 s requirement [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figures from the paper (13 more)
Figure 4
Figure 4. Figure 4: Example of a settling time failure in y position. The y axis is the one exposed to larger stresses from gravitational loads [PITH_FULL_IMAGE:figures/full_fig_p005_4.png]
Figure 5
Figure 5. Figure 5: Reference axes for the telescope system. [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]
Figure 6
Figure 6. Figure 6: Braking distance is polynomially proportional to the TMA speed. [PITH_FULL_IMAGE:figures/full_fig_p007_6.png]
Figure 7
Figure 7. Figure 7: Example of the bump test on actuator 112, both on Z and X axes. [PITH_FULL_IMAGE:figures/full_fig_p008_7.png]
Figure 8
Figure 8. Figure 8: Histogram of failing FAs during three periods. Period 1: 2024 October to 2025 March (Blue, ComCam [PITH_FULL_IMAGE:figures/full_fig_p009_8.png]
Figure 9
Figure 9. Figure 9: Treemap of failing FAs during three periods. The sequential colours indicate Period 1: 2024 October [PITH_FULL_IMAGE:figures/full_fig_p009_9.png]
Figure 10
Figure 10. Figure 10: Transition of the measured forces on each hardpoint when the TMA is at el = 1deg [PITH_FULL_IMAGE:figures/full_fig_p010_10.png]
Figure 11
Figure 11. Figure 11: Both plots show high stiffness values during 2023 and 2024 [PITH_FULL_IMAGE:figures/full_fig_p011_11.png]
Figure 12
Figure 12. Figure 12: Dashboard of hardpoint stiffness trends since January 2023 to April 2026. HP1: blue, HP2: orange, [PITH_FULL_IMAGE:figures/full_fig_p012_12.png]
Figure 13
Figure 13. Figure 13: Standard deviation for each hp since 2025. [PITH_FULL_IMAGE:figures/full_fig_p013_13.png]
Figure 14
Figure 14. Figure 14: Example of M1M3 HP forces when earthquake happened in 2025 November 15. [PITH_FULL_IMAGE:figures/full_fig_p014_14.png]
Figure 15
Figure 15. Figure 15: Comparing two events of earthquakes that happened in March 13 (top) and March 09, 2026 to show [PITH_FULL_IMAGE:figures/full_fig_p016_15.png]
Figure 16
Figure 16. Figure 16: Comparing position xyz and rotation rxryrz after the earthquakes on March 13 when the reaction to [PITH_FULL_IMAGE:figures/full_fig_p017_16.png]

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Reference graph

Works this paper leans on

16 extracted references · 16 canonical work pages

  1. [1]

    Lsst: from science drivers to reference design and anticipated data products,

    Željko Ivezić et.al, “Lsst: from science drivers to reference design and anticipated data products,” The Astrophysical Journal 873(2), 111 (2019)

    work page 2019

  2. [2]

    The LSST commissioning camera status and progress,

    James Howard et.al, “The LSST commissioning camera status and progress,” in [ Ground-based and Airborne Telescopes VII], Marshall, H. K. and Spyromilio, J., eds., 10700, 107003D, International Society for Optics and Photonics, SPIE (2018)

    work page 2018

  3. [3]

    Design and development of the 3.2 gigapixel camera for the Large Synoptic Survey Telescope,

    S. M. Kahn et.al, “Design and development of the 3.2 gigapixel camera for the Large Synoptic Survey Telescope,” in [ Ground-based and Airborne Instrumentation for Astronomy III ], McLean, I. S., Ramsay, S. K., and Takami, H., eds., 7735, 77350J, International Society for Optics and Photonics, SPIE (2010)

    work page 2010

  4. [4]

    Rubin M1M3 support system dynamic performance,

    Quint, B. C., Daruich, F., Kubánek, P., Neill, D. R., Megias, G., Shestakov, A., Shugart, A., Jeremie, A., Levine, B., Stalder, B., Lage, C., Sanmartim, D., Boutigny, D., Urbach, E., Dennihy, E., Arancibia, F. M., Drass, H., Park, H., Sevilla-Noarbe, I., Sotuela, I., Sebag, J., Hernández, J., Carlin, J., Aubel, K., Fanning, K., Reil, K., Cipriano, L. T. S...

    work page 2026

  5. [5]

    Final design of the LSST primary/tertiary mirror cell assembly,

    Neill, D. R., Muller, G., Hileman, E., DeVries, J., Araujo, C., Gressler, W. J., Lotz, P. J., Mills, D., Sebag, J., Thomas, S., Warner, M., and Wiecha, O., “Final design of the LSST primary/tertiary mirror cell assembly,” in [ Ground-based and Airborne Telescopes VI ], Hall, H. J., Gilmozzi, R., and Marshall, H. K., eds., 9906, 99060Q, International Socie...

    work page 2016

  6. [6]

    Lsst m1m3 figure actuator final design, fabrication, and test,

    Muller, G. P., Hileman, E. A., Daruich, F., Warner, M., Wiecha, O. M., Araujo, C., Mills, N., Johnson, B. E., Stover, E., Booth, M. T., et al., “Lsst m1m3 figure actuator final design, fabrication, and test,” in [Ground-based and Airborne Telescopes VII ], 10700, 1224–1242, SPIE (2018)

    work page 2018

  7. [7]

    LSST hardpoints final design, fabrication, and test,

    Booth, M. T., Clements, A., and Johnson, B., “LSST hardpoints final design, fabrication, and test,” in [Ground-based and Airborne Telescopes VII ], Marshall, H. K. and Spyromilio, J., eds., Society of Photo- Optical Instrumentation Engineers (SPIE) Conference Series 10700, 107003S (July 2018)

    work page 2018

  8. [8]

    The Large Binocular Telescope primary mirror support control system description and current performance results,

    Ashby, D. S., Kern, J., Hill, J. M., Davison, W. B., Cuerden, B., Brynnel, J. G., Biddick, C., and Duffek, K., “The Large Binocular Telescope primary mirror support control system description and current performance results,” in [ Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation ], Atad- Ettedgui, E. and Lemke, D., eds., Soci...

    work page 2008

Show all 16 references
  1. [9]

    Simonyi Survey Telescope M1M3 control system,

    Petr Kubánek et.al, “Simonyi Survey Telescope M1M3 control system,” in [ Software and Cyberinfrastructure for Astronomy VII ], Ibsen, J. and Chiozzi, G., eds., 12189, 121890H, International Society for Optics and Photonics, SPIE (2022)

    2022

  2. [10]

    LSST telescope modeling overview,

    J. Sebag et.al, “LSST telescope modeling overview,” in [ Modeling, Systems Engineering, and Project Man- agement for Astronomy VII ], Angeli, G. Z. and Dierickx, P., eds., 9911, 99112E, International Society for Optics and Photonics, SPIE (2016)

    2016

  3. [11]

    Baseline design of the LSST telescope mount assembly,

    Douglas R. Neill et.al, “Baseline design of the LSST telescope mount assembly,” in [ Ground-based and Airborne Telescopes V ], Stepp, L. M., Gilmozzi, R., and Hall, H. J., eds., 9145, 914518, International Society for Optics and Photonics, SPIE (2014)

    2014

  4. [12]

    Active optics control development at the lbt,

    Ashby, D. S., Biddick, C., and Hill, J. M., “Active optics control development at the lbt,” in [ Ground-based and Airborne Telescopes V ], 9145, 1051–1066, SPIE (2014)

    2014

  5. [13]

    Determining stress-based bending mode limits for the vera c. rubin observatory m1m3 active mirror system,

    Malhar et.al, “Determining stress-based bending mode limits for the vera c. rubin observatory m1m3 active mirror system,” in [ Ground-based and Airborne Telescopes XI ], 14147, in press, International Society for Optics and Photonics, SPIE (2026)

    2026

  6. [14]

    Telescope testing with active m1m3/m2 cells: mass balance and dynam- ics performance during the commissioning of vera c. rubin observatory,

    Freddy Muñoz Arancibia et.al, “Telescope testing with active m1m3/m2 cells: mass balance and dynam- ics performance during the commissioning of vera c. rubin observatory,” in [ Ground-based and Airborne Telescopes XI], 14147, in press, International Society for Optics and Phot...

    2026

  7. [15]

    Rubin Observatory Simonyi Survey Telescope integrated mount performance,

    Stalder, B., Munoz, F., Aguilar, C., Araya, C., Aubel, K., Barr, J., Borstad, A., Claver, C., Clements, A. W., Constanzo, J., Corvetto, G., Coughlin, E., Daruich, F., Dennihy, E., Drass, H., Esteves, J., Fábrega, J., Fanning, K., Ferguson, P., Fernandez, M. G., Fernandez, M., ...

    2024

  8. [16]

    Lsst m1m3 active mirror support system optimized to accommodate rapid telescope motions,

    Felipe Daruich et.al, “Lsst m1m3 active mirror support system optimized to accommodate rapid telescope motions,” in [ Ground-based and Airborne Telescopes VII ], 10700, 1091–1106, SPIE (2018)

    2018

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Reviewed July 2, 2026 · model on record in the stance chip above.