LOG OF ADJUSTMENTS TO SIGMA TAU MASER AT GREEN BANK
Model NAV-2001, serial # 105-17
(INTERFEROMETER CONTROL BUILDING.)
Maser moved to Reber Lab: GBT equipment room, Oct 29, 1998.
-------------------------------------------------------------

Date Changed          Synthesizer**    1PPS delay      new ST-GPS  Remarks
-----------------  ---------------    ------------   ------------  ------------------
pre-July23, 1992       31045259           ?     
July 23, 1992          31037403        925257          -0.20 us    1pps counter power off.
Sep 20, 1993 1230UT       "            028424
Dec 3, 1993            31034000        028426
Dec 16, 1993           31030000          "
Jan 6, 1994            31025000          "
Jan 31, 1994              "            028427          +0.39 us
May 03, 1994           31023000        028428          +0.20 us
May 19, 1994              "            404062          +0.80 us   Batteries replaced.
Aug 08, 1994 2020UT       "            935840	       +0.52 us   Power off to 1PPS counter.
Aug 09, 1994 1330UT    31016200          "  

Oct 13, 1994 1330UT (867,210,162,00)     "                        Offset 10-8 ##
Oct 14, 1994 1730UT (869,310,162,00)   934859          +0.11 us   restore to original state.

Dec 09, 1994 4-16 UT      "              "             +1.5 us    Cavity register adjust. #3
Feb 22, 1995 1843UT (867,210,162,00)     "                        Offset 10-8 #4
Feb 23, 1995        (869,310,162,00)     -                        Restore to original synthesizer setting.
Mar 10,95                                              +35us      Site 1Hz offset
Mar 20,95                 "                            -50ns      Site1Hz adjusted.
Dec 6,95   19:49UT   86,716,377,865                               Offset 10-8 (#5)
Dec 7,95   21:42UT   86,931,004,000                   -922us      Adjust rate (#6)
Dec 7,95   21:45UT        "                            0.2us      Adjust offset (#7)              
May 17,96                 "                                       OFFSET ADJUST(#8)
May 22,96  21:19UT   86,716,365,666                               Change rate by 10-8 for GBTIES3 run.
May 23,96 21:36UT    86,931,004,000                               Restore rate.
Oct 22,96 17:07UT    86,930,991,200                               Adjust rate to match GPS.
Jan 2, 98 15:28UT    86,930,983,000                               Decrease rate to match GPS.

Oct 29, 98:          no change                                    Move equipment to Reber Lab: GBT equipment room.

March 25, 2002:	     no change					  Adjust VCO voltage to near 0
                                                                  (was > 1 volt)
April 5, 2002        86,930,981,000                               Decrease rate to match GPS. (#9)

April 13, 2004       no rate change                     ~50ns     Adjust offset of TRAK master clock
                                                                   (previously offset was ~500ns
---------------------------------------------------------------------------------
 ** NOTE: 3 high order digits omitted from synthesizer listing, 
	for example, the first line would read in full: 869 3104 5259

 ## Offset maser rate by .05HZ(at 5MHZ) for NAPS2 VLBI run involving both
	the 140-ft and 85-3.

 #3 Dec 9, 1994.  Sigma Tau engineers adjusted the cavity servo to bring the
	cavity register into nominal range.  Offset ST-GPS changed from
	about +0.8 to +1.5 us.  Synthesizer and 1PPS delay not changed.

 #4 Offset maser rate by -.05HZ(at 5MHZ) for GBTIES VLBI run involving 
	the 140-ft, 85-3, and the new 20-meter.

 #5 Offset maser by -0.05Hz at 5MHz for GBTIE2 run including 140-ft,
	85-3, and 20-meter.

 #6 Adjust rate to approximate GPS.  Offset grew to -922us while running at
	offset rate (#5).

 #7 Adjust Site 1pps offset to be close to GPS.
 
 #8 TRAK lost time due to power glitch.  Maser rate not affected.
	TRAK 1pps adjusted.

 #9 Rate Site1Hz to TAC was +8.57 ns/day for the year of 2001.
    Decreased synthesizer by 2000 counts, corresponding to 8.05 ns/day.