HET End-Trimester Report
Third Period of 2021
August 1 - November 30

• Facility Status
• Observing Statistics
• Observing Programs Status
• Institution Status
• TAC Response

• HPF:
• The HPF vacuum-jacketed LN2 lines were pumped and low-precision targets only were observed on a few nights. A few nights were also low-precision only because of LFC issues
• Aug 2-6 the HPF LFC team was on site doing maintenance and improvements including replacing UNe and Alpha Bright lamps; no impact to precision or observations
• In October it was realized that the HPF detector's bias/pedestal level had been creeping upward and we were losing dynamic range on the instrument. The graph below shows the trend since 2018. The A/D converter saturates at 65k so when the pedestal level is at 40k are lacking a significant amount of dynamic range.
• Nov 1-11 HPF was unavailable for science for detector engineering work (bias pedestal level resetting). The pedestal level was reset to ~12k but is rising again. We expect this solution to buy us a little more time, and to deal with a large pedestal level again in 4-6 months.
  

• Facility:
• Nearly-normal operations have returned with very few COVID-19 procedures in place. All observations have been conducted full in-person in the control room since July 2021. We retain the ability for the RA and/or TO to observe remotely, but have not needed to exercise that option in the 21-3 period.
• Wavefront Sensor 1 (WFS1) went offline October 17th due to a mechanical/electrical issue, and we have relied solely on WFS2 in the mean time.
  

The following tables give a break down of all attempted science visits as well as the category that each falls into.

Charged exposures
Number of Times	Shutter Open (Hours)	Type
3635	526.80	A - Acceptable
59	14.70	B - Acceptable but Border line conditions
470	129.23	4 - Priority 4 visits (does not include 1/2 charge)
0	0.0	Q - charged but PI error
0	0.0	C - Acceptable by RA but PI rejects

Uncharged exposures caught by RA
Number of Times	Shutter Open (Hours)	Type
0	0.00	N - Rejected due to unknown cause
23	4.82	E - Rejected for Equipment Failure
228	52.77	W - Rejected for Weather
27	6.03	H - Rejected for Human Errors

Uncharged exposures caught by PI
Number of Times	Shutter Open (Hours)	Type
15	4.45	P - Rejected for weather
0	0.00	F - Rejected for Equipment Failure
4	0.95	T - Rejected for poor track choice
0	0.00	X - Rejected for Human failure

Acceptable but Uncharged exposures
Number of Times	Shutter Open (Hours)	Type
0	0.0	I - Targets observed under otherwise idle conditions

The following setup statistics include slew, acquisition, and starting data collection script. The table below gives the average setup time for each instrument PER ACTUAL VISIT and the average and maximum COMPLETED charged science exposures and visits.

The "Exposure" is defined by when the (CCD) shutter opens and closes. A "Visit" is the requested total CCD shutter open time during a track and might be made up of several "Exposures". "Visit" as defined here contains no overhead. To calculate one type of observing efficiency metric one might divide the "Visit" by the sum of "Visit" + "Overhead".

The average setup per visit is calculated from acceptable priority 0-3 (not borderline) science targets. This number reflects how quickly we can move from object to object on average for each instrument, however, this statistic tends to weight the setup for programs with large number of targets.

The average overhead percentage is calculated for each instrument and shows how much of that instrument's total time on sky (overhead+exposure) was overhead. NB: LRS2 has the smallest overhead %, but typical LRS2 observations use much longer exposures than VIRUS, even though VIRUS has a faster average setup time.

Instrument	Avg Setup per Visit (min)	Total time exposed (hrs)	Overhead %
VIRUS	4.48	133.45	24.80%
LRS2	5.79	98.40	29.49%
HPF	6.81	214.27	30.68%

The setup statistics can be shortened by multiple setups (each one counted as a separate visit) while on the same target such as moving from LRS2-B to LRS2-R.

Within the times when HETDEX shots were available on-sky for >20 minutes, the following percentages summarize how the time was used:

• 46.7% HETDEX (36.6% exposures, 10.1% overhead)
• 30.9% weather losses
  
• 19.2% sci/GTO/eng/comm (1.44% engineering/commissioning, 11.4% science/GTO exposures, 6.35% science/GTO overheads)
• 32.2% at P0 (17.1h)
• 19.9% at P1 (10.6h)
• 10.1% at P2 (5.4h)
• 16.6% at P3 (8.8h)
• 21.2% at P4 (11.3h)
  
• 1.3% mirror alignment
• 1.9% problems

Overall time charged: 225.9 (eng/comm/GTO) + 394.17h (sci) = 620.07h
Total estimated science time available (in TAC time determinations): 609.54h
   Conclusion: weather in 21-3 was slightly better than expected, resulting in high completion rates across programs/priorities.

Observing Programs Status

In the table below we show the breakdown of the charged time for each program submitted. The "Total %" is the completion of the entire TAC time including P4 time. The last four columns show the completion rate for targets submitted in each priority bin. This completion rate is the greater of the targets completed percentage and the TAC allocation completed percentage in each priority bin.

Program Completion Rates (sci only, removing NT/HC/TD)
Priority	Average Completion	Median Completion
P0	99.8%	100%
P1	100%	100%
P2	98.1%	100%
P3	95.0%	100%

NB great weather in the second half of the 21-3 trimester resulted in high completion rates for all priorities.

Institution Status

Below we show how the TAC allocations were determined.

This is how each institution had allocated its time by priority:

Time Allocation by Institution (hours)
Institution	Priority 0	Priority 1	Priority 2	Priority 3	Priority 4	Total P0-P3	Frac. of allowed
Goettingen	1.20	3.50	4.70	4.70	-	14.10	100.4%
Munich	1.70	5.30	6.90	6.90	-	20.80	99.8%
PSU	6.60	21.33	30.50	30.50	14.80	88.93	98.1%
UT	19.75	57.80	76.33	77.75	127.00	231.63	100.3%
Other allocations
GTO	163.5	13.00	8.00	3.00	9.00	187.50	100.0%

Notes:
1) Allocations in joint programs are reported separately for each partner

The following is a summary of the total charged time for each institution based on our htopx data base (for shutter open) and night reports (for overhead). It includes shutter open time (weighting priority four by half) and overhead (no overhead for priority 4 observations). Recently this calculation was re-derived using a deficit/surplus model. For each financial year the share paid is compared with the time charged - any discrepancy between the two is tracked and carried forward as a deficit. A negative deficit means more time was observed for that partner than their financial share; a positive deficit means less time was observed. These deficits are calculated in each previous financial year; the table below also includes a preliminary total for the current financial year so far.

Below are the summaries of the Guaranteed Time Observations (GTO) programs granted by the Board:

GTO and Special Time Charged by Project (hours)
Project	Allocated in 21-3	Allocated total to date including 21-3	Charged in 21-3	Charged total to date including 21-3
HETDEX (HETYY-P-100)	150.0	2314.0	148.1	1698.9
LRS2 GTO (HETYY-P-2XX)	8.0	183.9	8.8	109.9
HPF GTO (HETYY-P-3XX)	20.0	200.4	19.5	200.6
GW (HETYY-P-400)	0.0	70.0	0.0	12.4

(Totals to date start from the 11-2 period)

SJ, 5 Dec 2021