IMPORTANT message about HPF's RV precision

5 views

Skip to first unread message

Steven Janowiecki

unread,

Jun 17, 2021, 9:52:16 PM6/17/21

to het-p...@het.as.utexas.edu, HET Observations & Science Support, HET Astronomer, Greg Z, RA HET, Suvrath Mahadevan, Joe Philip Ninan, Bender, Chad - (cbender), Scott A. Diddams, George Damm, Connor Fredrick, Guðmundur Kári Stefánsson

Dear PIs with active HPF programs on the HET and partner TAC chairs,

We've had an issue this week with the HPF Laser Frequency Comb which may impact your observations. Below is a message from Suvrath Mahadevan, Principal Investigator of HPF:

The HPF laser frequency comb (LFC) has suffered a failure on Monday 14 Jun in its spatial light modulator compromising the flattening of the LFC spectrum. The LFC also underwent a deterministic frequency hop of 125MHz (~125m/s), induced by attempts to identify the issue, that has been fixed. A fix to the LFC is anticipated only on timescales of mid July. The HPF team feels that at a high confidence level using the HPF etalon for calibrations through the night will still enable nightly calibration precision to ~1m/s. Programs requiring RV precision at or better than 1m/s have the potential to be impacted and the PIs may wish to consider deferring their targets. Most programs should be largely unaffected, though precision RV reductions may take longer than normal. Targets needing "simultaneous calibration" with LFC can not be observed. As always there is always a risk at these extreme precisions that unanticipated effects may prevent 1m/s calibration, but our best estimate is that the HPF etalon will help us bridge through this gap till mid July without serious issues (though not without considerable work behind the scenes on our end).

Earlier this week we paused observations of all HPF targets with RVHIGHPREC=Y, but based on the HPF team's advice we are now resuming observations of HPF targets with RVHIGHPREC=Y. As Suvrath mentioned we still cannot observe targets which require simultaneous LFC calibrations (HPFCOMPARISON=LFC) until the LFC is back to normal.

If you do not wish for your targets to be observed in this mode, please defer them by logging into hydra.as.utexas.edu, changing their status in your program tab, and submitting those changes into the queue. We will resume all high-precision observations active in the queue starting tonight, June 17th, night of 2021-06-18 UT!

Let us know if you have any questions or concerns and we'll be happy to help make sure we get the best science for your programs as we possibly can.