short-term VIRUS downtime

[Steven Janowiecki]

Dear VIRUS PIs,

I'm writing to let you know about some unscheduled VIRUS downtime we're experiencing at the moment (further details below). Tonight VIRUS is offline but we expect some partial availability in the coming nights as the instrument comes back to full strength.

Whenever VIRUS is at least partially available we will continue observing VIRUS targets from the queue. If you wish to wait until VIRUS is returned to full operations, please defer your observations for the time being - we anticipate a return to normal on Saturday Feb 26th.

For any VIRUS targets which have specified VIFU in the Phase II TSL files, we will verify that the requested IFU is available before observing your target.

Let me know if you have any questions or if we can help.

Steven

---------- Forwarded message ---------
From: MacQueen, Phillip J <p...@astro.as.utexas.edu>
Date: Mon, Feb 21, 2022 at 5:50 PM
Subject: [Het-operations 023046] VIRUS is off line until Saturday Feb 26th
To: Discussions of HET operations issues <het-ope...@het.as.utexas.edu>, Karl Gebhardt <gebh...@astro.as.utexas.edu>
Cc: Trent Peterson <tr...@astro.as.utexas.edu>, Director Armandroff <dire...@astro.as.utexas.edu>

All,

This message is to let you know that VIRUS is powered down, off line,
and is not available tonight, February 21st.  One half of VIRUS is
likely to be back on line tomorrow night, February 22nd. We anticipate
that VIRUS will be fully back on line this Saturday night, February
26th, with a small chance of that being Sunday night.

As you know, two of our five VIRUS power supply filter boxes have had
fires inside them in recent times.  VIRUS uses four filter boxes when in
full operation.  Herman and I understand the failure mode, and we have
an upgrade strategy to prevent the problem that we have been
implementing.  One filter box is upgraded, one filter box is repaired,
upgraded, and en route to the observatory, one filter box is likely
destroyed, and the remaining two filter boxes are en route to Austin for
upgrade.

When VIRUS is powered back up tomorrow afternoon the CCDs will have
settled to their minimum temperatures.  It takes the CCD silicon
considerably long to warm up and stabilize at operating temperature that
it takes the CCD thermometers.  This is seen as a CCD bias drift.  Data
should not be taken until 5-6 hours after the CCD thermometers stabilize
at operating temperature.

Our current plan is to have half of side one and half of side two
powered up tomorrow night.  This will make the on-sky footprint look
approximately like half the VIRUS units have been powered down in a
random distribution.

Phillip and Herman

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[Steven Janowiecki]

Dear PIs of VIRUS programs,

I'm pleased to let you know that last night VIRUS returned to the full 78 units online as usual. Thanks to Phillip and Herman for the quick work to get things running again.

At this time you can go ahead and re-activate any deferred targets that you want to have observed with the full VIRUS array - it's good to have it back!

Steven