JCMT Pointing Event History

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Pointing

1992 Nov - antenna loading on central bearing changed
1993 Jan - elevation Encoder changed
1993 Jan - telescope focal length reduced 8mm
1993 Jul - new Nasmyth platform
1993 Aug - elevation encoder replaced
1993 Dec - antenna loading changed (central bearing)
1994 Jan - antenna loading changed (central bearing)
1994 Jan - second focal length change, 7.5mm
1994 Jun - cone bar wedges
1994 Jul - cone bar welding
1994 Aug - elevation encoder replaced
1994 Nov - antenna loading changed (central bearing)
1995 Jun - inclinometry azimuth resolution increased to 0.2^o near track joints
1995 Jun 09 - central bearing load adjustment
1995 Oct 12 - two azimuth track joints (4/5 , 6/7) regrouted, one (4/5) welded
1995 Nov - trial grouting of az-track
1995 Dec - (with hindsight) probable failure of right wheel
1996 Apr 01 - central bearing adjustment
1996 Apr 17 - rear right wheel replaced
1996 May - new, customized 24-bit encoders by BEI installed
1996 Jun - SCUBA installed on left Nasmyth - and counterweights on the right.
1996 Aug 19-23 - more track joints welded : 2/3, 3/4, 5/6, 9/10, 12/13, 13/14, 14/1
1997 Feb : start of 10MHz clock problems ?
1997 Feb : Central Bearing fault recognized. See also Firmin's recent analysis .
1997 Mar 10 : 10MHz reference now from GPS.
1997 Mar : Peculiar inclinometry - see reports .
1997 Apr 02 : Track inspected by Ian Pain. Report.
1997 Apr 09 : SCUBA pointing run
1997 Apr 10 : Joint 7/8 welded. Inclinometry done afterwards.
1997 Apr 17 : Joint 1/2 welded. Inclinometry done afterwards.
1997 Apr 30 : Introduction of TEMP_MEAN_SLOPE to correct elevation pointing.
1997 May 15 : Joint 8/9 welded. Inclinometry done, new track model installed.
1997 May 29 : Joint 11/12 welded. Inclinometry done, new track model installed.
1997 Jun 05 : Joint 6/7 welded. Inclinometry done, new track model installed.
1997 Sep 08 : temp_mean_slope disabled after 4 months experimentation.
1997 Dec 22 : Value of temp_slope changed to 8.6"/^oC.
1998 Apr 11 : Yaw calculated from inclinometry using fL = -fR = 1.21 instead of 0.83
1998 Apr 21 : Empirical correction for central bearing problem changed.
1998 June 10 : Central bearing loading adjusted
1998 June 23 : Value of temp_slope changed to 5.0"/^oC.
1998 Aug 31 : RLB.for changed in the way it it extrapolates
1998 Oct 27 : Central bearing load adjustment
1998 Nov 19 : Spare inclinometer mount bolted on L-A-frame.
1998 Dec 01 : some bolt-tightening on antenna structure : "a few loose bolts - mostly on the flange holding the elevation drive motor in place but also a few elsewhere"
1999 Mar 12 : Central bearing load adjustment(s)
1999 Mar 15 : Construction of counter balance weights platform (between front wheels) started.
1999 Mar 31 : Construction of counter balance weights platform completed.
1999 May 03 : Central bearing replacement starts.
1999 May 08 : Central bearing replacement ends ( report by IP ), c.b. load adjusted
1999 May 08 : 3t of weights added to front of carousel - see the photos !! ( 1, 2, 3, 4), and report by RJSG .
1999 June 01 : Value of temp_slope changed to 10.0"/^oC.
1999 Nov 05 : Value of yaw factor in makemodel.com changed from 1.21 to 1.00.
2000 Mar 13 : New carousel drives installed.
2000 Apr 12 : Value of temp_mean_slope changed to -1.0"/^oC.
2000 Apr 19 : Value of temp_slope changed to 6.0"/^oC.
2000 Apr 21 : Value of temp_mean_slope changed to 0.0"/^oC. - need for 20000412 change not convincing.
2000 May 16 : tel_empirical.dat resurrected to correct elevation pointing errors across transit.
2000 May 16 : p#2 of pointing model changed by -0.9" to match tel_empirical.dat.
2000 May 31 : pointing of 000529 suggests that sign of delta(p2) was wrong : new model installed.
2000 Jun 01 : temp_mean_slope changed to 0.9"/^o. TEL.ifl annotated for sign of change.
2000 Jun 06 - central bearing load adjustment.
2000 Jun 12 : temp_mean_slope changed to 0.3"/^o, following analysis of data from 09/10/11 June.
2000 Aug 24 : New TCS installed.
2000 Sep 21 : SMU z-axis failure. Repaired 6 days later
2000 Sep 22 : First inclinometry taken with new TCS reveals possible wheel defect.
2000 Sep 28 : new polynomial terms added to TPOINT model (by NPR) to correct approximations when near pole.
2001 Jan 02 : change temp_mean_slope to 0.8
2001 Jan 09 : First allsky pointing run using new TCS.
2001 Jan 10 : Relative pointing between RxB & RxW_D established
2001 Feb 01 : The usefulness of VirgoA is examined, OK.
2001 Feb 06 : Central bearing load ajustment.
2001 Apr 25 : Elevation encoder replaced.
2001 Jun 19 : algorithm installed to correct 'transit' effect.
2001 Jul 24 : change temp_mean_slope to 0.0
2001 Aug 29 : Old UKT14 tertiary mirror removed by Tomas Chylek
2001 Sep 06 : Inclinometry scales for TMU-Y & Spare-Y = 20.8mV/".
2001 Sep 24 : inclinometer mounted on flip-side of tertiary mirror.
2001 Oct 06 : First use of tiltable inclinometer.
2002 Jul 31 : a month's engineering, to install the K-mirror, ends. Pointing restored.
2002 Aug-Dec : pointing poor/worrisome.
2003 Feb 18 : Excellent pointing run
2003 Mar 10 : TMU drive broken, replaced, realigned
2003 Mar 11 : TMU drive broken again
2003 Mar 25 : 'fixed' TMU inclinometer #0354 replaced by 'spare', #2036.
2003 Apr 10 : erroneous application of F2 (track model term) discovered and corrected.
2003 Apr 12 : First hybrid track model installed
2004 Jan 26 : Description and summary of azimuth tracking fault Aug 2000 - Apr 2003 for JCMT user community.

Contact: Iain Coulson. Updated: Sun Jul 3 11:35:58 HST 2005

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