HET End-Trimester Report
Second Period of 2004
April 1 - July 31

NOTE: We are now using FWHM which is measured off both the LRS "pre" images and the FIF bent prime guider.

The following image quality statistics were taken from the statistics recorded for science operations in the night report.

For comparison here is the image quality for the same period of 2003

Here are the DIMM values reported in the night report.

Month by Month Summary

The following table gives the observing statistics for each month. The second column gives the fraction of the month that was spent attempting science (as opposed to engineering or instrument commissioning). Science time is defined to begin at 18 degree twilight or the first science target. Science time is defined to end at 18 degree twilight or the last science target. The fourth column gives the fraction of the possible science time (A) lost due to weather. The fifth through tenth columns give how the remaining science time (after removing weather losses) was spent. Please note that the first stack of the night often occurs before 18 degree twilight.

Month	A:Fraction of the Time that was Possible Science	B:Average Night Length	C:Fraction of Total Science Time Lost due to Weather	D:Fraction of Actual Science Time with Shutter Open	E:Fraction of Actual Science Time as Overhead	F:Fraction of Actual Science Time Lost due to Alignment	G:Fraction of Actual Science Time Lost due to Calibrations	H:Fraction of Actual Science Time Lost due to Problems	I:Fraction of Actual Science Time Not accounted for or Lost
April	0.926	8.22	0.38	0.44	0.30	0.03	0.08	0.02	0.13
May	0.917	7.20	0.26	0.50	0.27	0.04	0.04	0.08	0.08
June	0.935	6.66	0.39	0.49	0.26	0.02	0.05	0.09	0.09
July	0.979	6.97	0.30	0.53	0.31	0.04	0.01	0.07	0.04

The last column is new and acounts for all of the lost or not used minutes. Some of this time is accounting errors and some is time not charged to any program due to operations inefficiency.

Details on Nightly cloud cover based on the TO's observations of the sky reported 3 times a night in the night report.:

Month	Fraction of the Nights that were Clear	Fraction of the Nights that were Mostly Clear	Fraction of the Nights that were Partly Cloudy	Fraction of the Nights that were Mostly Cloudy	Fraction of the Nights that were Cloudy
April	0.50	0.10	0.23	0.10	0.07
May	0.52	0.10	0.23	0.10	0.07
June	0.10	0.23	0.23	0.17	0.17
July	0.19	0.29	0.23	0.13	0.16

Please note that the HET could be closed due to humidity, smoke or high dust count and still have a "Clear" statistic in the night report.

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

Charged exposures
Number of Times	Shutter Open (Hours)	Type
804	136.6	A - Acceptable
95	19.8	B - Acceptable but Border line conditions
626	98.0	4 - Priority 4 visits (does not include 1/2 charge)
8	0.2	Q - charged but PI error
0	0.0	C - Acceptable by RA but PI rejects

Uncharged exposures
Number of Times	Shutter Open (Hours)	Type
5	0.8	I - Targets observed under otherwise idle conditions
19	4.3	E - Rejected by RA for Equipment Failure
30	5.7	H - Rejected for Human failure
79	12.8	W - Rejected by RA for Weather
10	2.1	P - Rejected by PI and confirmed by RA
3	0.7	N - Rejected due to unknown cause

So this is a total of 25.6 hours of uncharged spectra with an additional possible 19.8 hours of spectra that may be rejected.

The following overhead statistics include slew, setup, readout and refocus between exposures (if there are multiple exposures per visit). In the summary page for each program the average setup time is calculated. The table below gives the average setup time for each instrument PER VISIT and the average and maximum COMPLETED science exposures and visits.

The "Exposure" is defined by when the CCD 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 overhead per actual visit is the overhead for each acceptable priority 0-3 (not borderline, and with overheads > 4 minutes to avoid 2nd half of exposures with unrealisticly low overheads) science target. This number reflects how quickly we can move from object to object on average for each instrument, however, this statistic tends to weight the overhead for programs with large number of targets such as planet search programs.

The average overhead per requested visit is the total charged overhead per requested priority 0-3 visit averaged per program. To get this value we average the average overhead for each program as presented in the program status web pages. The average overhead per visit can be inflated by extra overhead charged for PI mistakes (such as bad finding charts or no targets found at sky detection limits) or for incomplete visits e.g. 2 visits of 1800s are done instead of 1 visit with a CRsplit of 2. The average overhead per visit can be deflated by the 15 minute cap applied to the HRS and MRS. This method tends to weight the overhead to programs with few targets and bad requested visit lengths, ie. very close to the track length.

Instrument	Avg Overhead per Actual Visit(min)	Avg Charged Overhead per Requested Visit(min)	Avg Exposure (sec)	Median Exposure (sec)	Max Exposure (sec)	Avg Visit (sec)	Median Visit (sec)	Max Visit (sec)
LRS	13.2	19.5	638.7	600	2400	1066.0	600	6300
HRS	9.3	10.6	621.5	560	2700	768.1	660	3600
MRS	10.6	8.6	1056.1	900	1800	1290.2	1200	2100

NOTE: AS OF 2003-3 THE SETUP TIME FOR AN ATTEMPTED MRS OR HRS TARGET IS CAPPED AT 15 MINUTES.

The overhead statistics can be shortened by multiple setups (each one counted as a separate visit) while on the same target as is the case for planet search programs. The overhead statistics can be lengthened by having multiple tracks that add up to a single htopx visit as can happen for very long tracks where each attempt might only yield a half visit.

A way to improve the overhead accumulated for programs with long exposure times is to add double the above overhead to the requested visit length and make sure that time is shorter than the actual track length. This avoids the RA having to split requested visits between several different tracks.

The following is a histogram of the current HET queue visits for the rest of the period. A line has been drawn at the expected number of hour long visits that we hope to achieve in each hour bin.

The following histogram shows some of the extrema in observing conditions: good seeing dark time, bright time and bad seeing dark time. A line has been drawn at the expected number of hour long visits that we hope to achieve in each hour bin.

The following histogram shows the bright time priority 0-3 contribution from each partner. The dashed line is a rough estimate of the number of hour long visits one could complete during the remainder of the period.

The following histogram shows the dark time priority 0-3 contribution from each partner. The dashed line is a rough estimate of the number of hour long visits one could complete during the remainder of the period.

From the above plots I have determined that:

• Then only remaining Priority 1 target was a synoptic TOO SN added very late in the period.
• The only remaining Priority 2 target was a single STA object.
• Most of the bright P<3 targets are the synoptic TOO SN added very late in the period.
• The only remaining dark time objects, good or bad seeing, are P4.