Reference for sidereal tracking only with the Simonyi Survey Telescope


It came up in the SCOC TOO workshop/proposal that Rubin will not be commissioned with the Simonyi Survey Telescope able to track non-sidereally. The public year 1/commissioning plan documents don’t explicitly include non-sidereal tracking. The SSSC has informally known this/expected this based on discussions with our DM liaison, but I can’t find a reference that explicitly states Simonyi Survey Telescope will not have non-sidereal tracking capability.

Some SSSC members were wondering if its not explicitly ruled out that this mode could be commissioned in the future. I am not sure if that is possible. I imagine this will come up against whenever there are potential updates/tweaks to the observing cadence. Is there a reference I can refer to my collaboration members to in the future about non-sidereal tracking and the Simonyi Survey Telescope ?


Hi Meg, thanks for this question.

I haven’t found a document stating that the telescope will not have non-sidereal tracking during commissioning and early science. But I did find the relevant requirement for the telescope to be able to track non-sidereally. As I understand it, since a requirement exists, this mode is not ruled out for the future.

In Document LSE-30, Observatory System Specifications, Section Non-Sidereal Tracking (OSS-REQ-0380; page 262) contains the requirement for the telesscope to track non-sidereally and quotes the angular rates that the telescope should be capable of (220 arcsec/sec), and the maximum tracking error (0.5 arcsec/min). The following section contains a restriction that regions in which non-sidereal tracking is used must be pre-approved by NSF and DOE.

This requirement is also quoted in Section B.8 of DMTN-056 on Special Programs, but without any additional information. Perhaps if more details would be relevant and help with survey strategies, I could add them to DMTN-065.

Hopefully this is the info you were looking for? Further questions always welcome.

My understanding was that @rblum5 stated there will be no non-sidereal tracking for TOOs at the SCOC TOO workshop in Year 1, so I think it would be helpful to have something in a commissioning document that clarifies what will be delivered in terms of non-sidereal tracking for year 1/commissioning from now to end of 2026 so the community has an expectation. Maybe that can go into RTN-011 or the commissioning documents?

Note that the agencies have placed restrictions on non-sidereal tracking, with pre-approval required for some parts of the sky. See number 6 of the list in the introduction of DMTN-199:

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Thanks Meg, yes I think we can get this statement into a citable document (probably RTN-011 as you mention) – we’ll be back in touch in a couple weeks.

Thanks, @MelissaGraham

Hi @MelissaGraham, @mschwamb ,
Just following up on this thread to see if Meg’s statement about non-sidereal tracking for year 1/commissioning was able to get incorporated in RTN-011.

See post: RTN-011 v5.1: Rubin Plans for an Early Science Program – a new version of RTN-011 has been issued clarifying the project’s position on non-sidereal tracking.