Subject: [Cbor] MJD (Fwd: Bulletin B number 387)

From: Carsten Bormann <[email-masked]>
Date: Wed, 3 Jun 2020 18:09:49 +0200

Today, we had a brief discussion about MJD, modified Julian dates.

Just as a random example of the use of MJD in the fundamental gears that keep our timekeeping going:
The International Earth Rotation Service (IERS) sends out bulletins regularly that explain how the earth moves and what that means for Sun position based timekeeping (UT1) vs. atomic time keeping (TAI).
This is needed for any astronomy that tries to use TAI-based time sources (e.g., GPS), as well as for the decision when to insert leap seconds (which is based on IERS data).
They give this information for each date so you can retroactively adjust what you saw in your telescope.
The dates are given in Gregorian form, e.g., 2020-04-01, but also (more usefully for astronomers) in MJD, here 58940.

Now if you know that (Time.parse("2020-04-01T00:00:00+00:00").utc-Time.parse('1970-01-01T00:00:00+00:00').utc)/86400.0 => 18353.0, you can add that to the MJD of 40587 for the UNIX epoch, and unsurprisingly you get: 58940.  Oh, and today it’s 59003 (Date.today.mjd).

I’m still looking for a citable reference from 1957, when Smithsonian Astrophysical Observatory (SAO) invented MJD by subtracting 2400000.5 from JD (introduced by Joseph Scaliger in the 16th century based on January 1, 4713 B.C.) to be able to track Sputnik efficiently on a 36-bit IBM 704 computer (using 18 bits for the date and the other 18 bits for the time of day).

We may want to pick this subject up again when discussing 63-bit absolute time with 100 ns granularity :-) or some such...

Grüße, Carsten

> Begin forwarded message:
> 
> From: [email-masked] (IERS EOP Product Center)
> Subject: Bulletin B number 387
> Date: 2020-05-04 at 22:35:31 CEST
> To: [email-masked]
> Reply-To: [email-masked] (IERS EOP Product Center)
> 
>                                                                BULLETIN B 387
>                                        			4 May 2020   
> 
> Contents are described in ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.pdf 
> 	
> 1 - DAILY FINAL VALUES OF x, y, UT1-UTC, dX, dY
> Angular unit is milliarcsecond (mas), time unit is millisecond (ms). 
> Upgraded solution from March 1 2017 - consistent with ITRF 2014.
> 
>       DATE     MJD       x       y      UT1-UTC      dX     dY     x err    y err   UT1 err  dX err  dY err
>    (0 h UTC)            mas     mas       ms         mas    mas     mas      mas      ms     mas     mas
> 
> Final values 
> 
> Mean formal error      0.053    0.038    0.0065    0.025  0.055 
> 
> 2020   3   2   58910   27.052  357.171 -205.5930    0.061 -0.015    0.056    0.039    0.0095  0.070  0.088
> 2020   3   3   58911   26.374  359.002 -206.1635    0.090 -0.029    0.056    0.039    0.0094  0.071  0.089
> 2020   3   4   58912   26.040  360.668 -206.6763    0.090 -0.006    0.056    0.039    0.0093  0.071  0.088
> 2020   3   5   58913   26.271  362.020 -207.1658    0.083  0.026    0.056    0.039    0.0092  0.072  0.087
> 2020   3   6   58914   26.971  363.910 -207.6964    0.075  0.058    0.056    0.039    0.0089  0.070  0.083
> 2020   3   7   58915   27.743  365.695 -208.3559    0.049  0.050    0.056    0.039    0.0087  0.071  0.081
> 2020   3   8   58916   28.156  367.442 -209.2279    0.016  0.026    0.056    0.038    0.0081  0.066  0.075
> 2020   3   9   58917   28.068  369.116 -210.3544   -0.017  0.003    0.055    0.038    0.0077  0.067  0.073
> 2020   3  10   58918   28.186  370.679 -211.7167   -0.050 -0.020    0.055    0.039    0.0075  0.067  0.071
> 2020   3  11   58919   28.655  372.325 -213.2290   -0.012  0.001    0.055    0.039    0.0073  0.067  0.068
> 2020   3  12   58920   29.168  373.782 -214.7503    0.045  0.034    0.055    0.039    0.0071  0.067  0.065
> 2020   3  13   58921   30.390  375.474 -216.1386    0.102  0.067    0.054    0.039    0.0069  0.067  0.063
> 2020   3  14   58922   31.837  377.519 -217.2921    0.092  0.111    0.054    0.039    0.0067  0.064  0.057
> 2020   3  15   58923   33.166  379.483 -218.1787    0.059  0.160    0.053    0.038    0.0062  0.059  0.053
> 2020   3  16   58924   34.196  380.925 -218.8244    0.026  0.209    0.053    0.038    0.0060  0.059  0.050
> 2020   3  17   58925   34.810  382.174 -219.2893   -0.007  0.257    0.052    0.038    0.0057  0.058  0.048
> 2020   3  18   58926   35.518  383.028 -219.6482   -0.015  0.152    0.052    0.038    0.0056  0.057  0.045
> 2020   3  19   58927   36.746  383.993 -219.9551   -0.016  0.005    0.052    0.038    0.0054  0.057  0.043
> 2020   3  20   58928   38.706  385.063 -220.2542   -0.017 -0.143    0.051    0.038    0.0053  0.057  0.041
> 2020   3  21   58929   40.911  386.045 -220.5675   -0.013 -0.159    0.051    0.038    0.0052  0.057  0.040
> 2020   3  22   58930   42.767  387.279 -220.9353   -0.008 -0.127    0.051    0.038    0.0051  0.057  0.038
> 2020   3  23   58931   43.796  388.552 -221.3969   -0.002 -0.096    0.050    0.038    0.0049  0.057  0.037
> 2020   3  24   58932   44.596  389.940 -221.9350    0.004 -0.064    0.050    0.038    0.0048  0.056  0.035
> 2020   3  25   58933   44.822  391.441 -222.4998   -0.025 -0.023    0.050    0.038    0.0048  0.056  0.036
> 2020   3  26   58934   44.447  393.068 -223.0586   -0.062  0.021    0.050    0.038    0.0049  0.057  0.037
> 2020   3  27   58935   43.820  394.134 -223.5768   -0.099  0.065    0.051    0.038    0.0050  0.057  0.037
> 2020   3  28   58936   44.678  395.036 -224.0270   -0.091  0.067    0.051    0.038    0.0051  0.057  0.038
> 2020   3  29   58937   45.811  396.474 -224.3985   -0.065  0.053    0.051    0.038    0.0052  0.058  0.038
> 2020   3  30   58938   47.066  397.981 -224.6996   -0.039  0.038    0.051    0.038    0.0052  0.058  0.039
> 2020   3  31   58939   48.786  399.658 -224.9459   -0.013  0.024    0.052    0.038    0.0053  0.059  0.039
> 2020   4   1   58940   50.873  401.240 -225.1677   -0.019 -0.007    0.052    0.038    0.0054  0.060  0.040
> 
> Preliminary extension 
> 2020   4   2   58941   52.629  403.274 -225.4275   -0.033 -0.043    0.053    0.038    0.0056  0.060  0.041
> 2020   4   3   58942   54.045  405.201 -225.8108   -0.047 -0.080    0.053    0.039    0.0057  0.061  0.042
> 2020   4   4   58943   54.939  406.879 -226.4131   -0.042 -0.057    0.054    0.039    0.0059  0.062  0.043
> 2020   4   5   58944   55.448  407.948 -227.3108   -0.030 -0.013    0.054    0.039    0.0060  0.062  0.044
> 2020   4   6   58945   55.942  408.915 -228.5296   -0.018  0.032    0.055    0.039    0.0061  0.063  0.045
> 2020   4   7   58946   56.202  409.418 -230.0133   -0.005  0.076    0.055    0.039    0.0063  0.064  0.046
> 2020   4   8   58947   56.867  409.951 -231.6181    0.038  0.012    0.055    0.040    0.0064  0.064  0.046
> 2020   4   9   58948   57.726  410.982 -233.1940    0.089 -0.080    0.056    0.040    0.0065  0.065  0.046
> 2020   4  10   58949   58.113  412.055 -234.6309    0.079 -0.071    0.056    0.040    0.0067  0.066  0.047
> 2020   4  11   58950   58.566  412.943 -235.7588    0.046 -0.024    0.057    0.040    0.0068  0.067  0.049
> 2020   4  12   58951   59.057  414.030 -236.6098    0.013  0.022    0.057    0.041    0.0069  0.068  0.050
> 2020   4  13   58952   59.805  415.374 -237.2074   -0.019  0.069    0.058    0.042    0.0070  0.069  0.052
> 2020   4  14   58953   60.918  416.776 -237.5996   -0.052  0.116    0.059    0.042    0.0071  0.070  0.053
> 2020   4  15   58954   62.146  418.046 -237.8591   -0.085  0.163    0.060    0.043    0.0072  0.071  0.055
> 2020   4  16   58955   62.853  419.714 -238.0355    0.036  0.069    0.062    0.045    0.0075  0.072  0.058
> 2020   4  17   58956   63.924  421.358 -238.2368    0.199 -0.062    0.064    0.046    0.0078  0.073  0.062
> 2020   4  18   58957   64.490  423.077 -238.5501    0.000  0.000    0.066    0.048    0.0081  0.075  0.067
> 2020   4  19   58958   64.316  424.255 -239.0153    2.224  1.502    0.047    0.031    0.0079  0.041  0.039
> 2020   4  20   58959   63.747  425.151 -239.4957    3.387  2.493    0.048    0.032    0.0082  0.042  0.042
> 2020   4  21   58960   63.142  425.931 -239.9896    4.549  3.484    0.049    0.033    0.0085  0.043  0.045
> 2020   4  22   58961   63.226  426.511 -240.4778    1.970  1.158    0.050    0.033    0.0088  0.500  0.500
> 2020   4  23   58962   64.174  427.385 -240.9283    1.327  0.785    0.050    0.034    0.0091  0.500  0.500
> 2020   4  24   58963   65.452  428.308 -241.3520    0.757  0.463    0.051    0.034    0.0094  0.500  0.500
> 2020   4  25   58964   67.020  429.350 -241.6901    0.487  0.318    0.052    0.035    0.0097  0.500  0.500
> 2020   4  26   58965   68.387  430.786 -241.8633    0.536  0.347    0.053    0.035    0.0100  0.500  0.500
> 2020   4  27   58966   69.326  432.013 -241.9663    0.738  0.445    0.054    0.036    0.0103  0.500  0.500
> 2020   4  28   58967   70.543  432.912 -242.0334    0.882  0.492    0.055    0.037    0.0107  0.500  0.500
> 2020   4  29   58968   72.198  433.759 -242.1119    0.858  0.442    0.056    0.037    0.0111  0.500  0.500
> 2020   4  30   58969   74.118  434.658 -242.2219    0.714  0.341    0.057    0.038    0.0115  0.500  0.500
> 2020   5   1   58970   75.783  435.916 -242.4483    0.586  0.275    0.058    0.039    0.0119  0.500  0.500
> 
> 	
> 2 - DAILY FINAL VALUES OF CELESTIAL POLE OFFSETS dPsi1980 & dEps1980
>  dPsi1980   dEps1980 ....dPsi,dEps / IAU 1980 precession-nutation model      
> Description : ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.pdf
> The Reference Systems are described in the 2006 IERS Annual Report.
> 
>       DATE     MJD    dPsi1980   dEps1980  sig dPsi  sig dEps   
>    (0 h UTC)             mas        mas      mas       mas   
> 
> 2020   3   2   58910  -107.618    -8.141     0.176     0.088
> 2020   3   3   58911  -107.667    -8.239     0.178     0.089
> 2020   3   4   58912  -107.675    -8.191     0.178     0.088
> 2020   3   5   58913  -107.792    -8.157     0.181     0.087
> 2020   3   6   58914  -108.125    -8.377     0.176     0.083
> 2020   3   7   58915  -108.350    -8.872     0.178     0.081
> 2020   3   8   58916  -107.965    -9.254     0.166     0.075
> 2020   3   9   58917  -107.107    -9.201     0.168     0.073
> 2020   3  10   58918  -106.499    -8.856     0.168     0.071
> 2020   3  11   58919  -106.433    -8.568     0.168     0.068
> 2020   3  12   58920  -106.813    -8.530     0.168     0.065
> 2020   3  13   58921  -107.160    -8.597     0.168     0.063
> 2020   3  14   58922  -107.352    -8.624     0.161     0.057
> 2020   3  15   58923  -107.339    -8.667     0.148     0.053
> 2020   3  16   58924  -107.299    -8.785     0.148     0.050
> 2020   3  17   58925  -107.403    -8.896     0.146     0.048
> 2020   3  18   58926  -107.525    -9.057     0.143     0.045
> 2020   3  19   58927  -107.478    -9.188     0.143     0.043
> 2020   3  20   58928  -107.167    -9.328     0.143     0.041
> 2020   3  21   58929  -106.746    -9.328     0.143     0.040
> 2020   3  22   58930  -106.488    -9.174     0.143     0.038
> 2020   3  23   58931  -106.488    -8.903     0.143     0.037
> 2020   3  24   58932  -106.628    -8.656     0.141     0.035
> 2020   3  25   58933  -106.814    -8.589     0.141     0.036
> 2020   3  26   58934  -106.872    -8.706     0.143     0.037
> 2020   3  27   58935  -106.797    -8.875     0.143     0.037
> 2020   3  28   58936  -106.602    -9.048     0.143     0.038
> 2020   3  29   58937  -106.510    -9.240     0.146     0.038
> 2020   3  30   58938  -106.577    -9.482     0.146     0.039
> 2020   3  31   58939  -106.605    -9.694     0.148     0.039
> 2020   4   1   58940  -106.503    -9.774     0.151     0.040
> 
> 
> 3 - EARTH ANGULAR VELOCITY : DAILY FINAL VALUES OF LOD, OMEGA AT 0hUTC
> 
> LOD     : Excess of the Length of day - 86400 s TAI 
> OMEGA   : Earth angular velocity  
> Description: ftp://hpiers.obspm.fr/iers/bul/bulb_new/bulletinb.pdf
> 
>    DATE        MJD     LOD     sigma      OMEGA           sigma        
> (0 h UTC)              ms       ms        mas/ms          mas/ms
> 
> 2020   3   2   58910  0.5935  0.0123  15.04106707535    0.00000000214 
> 2020   3   3   58911  0.5165  0.0124  15.04106708875    0.00000000216 
> 2020   3   4   58912  0.4635  0.0124  15.04106709798    0.00000000216 
> 2020   3   5   58913  0.5028  0.0125  15.04106709114    0.00000000218 
> 2020   3   6   58914  0.6226  0.0126  15.04106707028    0.00000000219 
> 2020   3   7   58915  0.8000  0.0123  15.04106703940    0.00000000214 
> 2020   3   8   58916  0.9841  0.0124  15.04106700735    0.00000000216 
> 2020   3   9   58917  1.2166  0.0124  15.04106696688    0.00000000216 
> 2020   3  10   58918  1.4868  0.0125  15.04106691984    0.00000000218 
> 2020   3  11   58919  1.5777  0.0126  15.04106690401    0.00000000219 
> 2020   3  12   58920  1.4394  0.0126  15.04106692809    0.00000000219 
> 2020   3  13   58921  1.2287  0.0127  15.04106696477    0.00000000221 
> 2020   3  14   58922  0.9841  0.0128  15.04106700735    0.00000000223 
> 2020   3  15   58923  0.7350  0.0125  15.04106705072    0.00000000218 
> 2020   3  16   58924  0.5614  0.0125  15.04106708094    0.00000000218 
> 2020   3  17   58925  0.4298  0.0126  15.04106710385    0.00000000219 
> 2020   3  18   58926  0.3245  0.0126  15.04106712218    0.00000000219 
> 2020   3  19   58927  0.2934  0.0127  15.04106712759    0.00000000221 
> 2020   3  20   58928  0.3209  0.0127  15.04106712281    0.00000000221 
> 2020   3  21   58929  0.3708  0.0128  15.04106711412    0.00000000223 
> 2020   3  22   58930  0.4059  0.0125  15.04106710801    0.00000000218 
> 2020   3  23   58931  0.4873  0.0126  15.04106709384    0.00000000219 
> 2020   3  24   58932  0.5568  0.0126  15.04106708174    0.00000000219 
> 2020   3  25   58933  0.5687  0.0127  15.04106707967    0.00000000221 
> 2020   3  26   58934  0.5606  0.0127  15.04106708108    0.00000000221 
> 2020   3  27   58935  0.4715  0.0127  15.04106709659    0.00000000221 
> 2020   3  28   58936  0.4307  0.0128  15.04106710369    0.00000000223 
> 2020   3  29   58937  0.3247  0.0128  15.04106712214    0.00000000223 
> 2020   3  30   58938  0.2583  0.0129  15.04106713370    0.00000000225 
> 2020   3  31   58939  0.2069  0.0129  15.04106714265    0.00000000225 
> 2020   4   1   58940  0.2524  0.0130  15.04106713473    0.00000000226 
> 
> 
> 4 - INFORMATION ON TIME SCALES 
> 
> 
>     TAI - UTC = 37 s.         during period [58910-58940]
> 
>     No leap second introduced during period [58910-58940]
> 
>     All information concerning time scales : 
> 	 - leap seconds announcements : Bulletin C 
> 	 - DUT1 announcements (UT1-UTC with 0.1 s accuracy) : Bulletin D
>      can be found at : 
>         - web site : http://hpiers.obspm.fr/eop-pc/
>         - anonymous ftp://hpiers.obspm.fr/iers/ 
> 
> 
> 5 - SUMMARY OF CONTRIBUTED EARTH ORIENTATION PARAMETERS SERIES
> This section gives the average precision of the individual series, some of them
> contributing to the combination (*) and their average agreement with it. 
> The period covered is that one of Bulletin B. 
> 
>    Units :  micro-arc-seconds for x/y/dX/dY        micro-seconds for UT1/LOD
> -----------------------------------------------------------------------------
>  EOP series             first line  : Mean  formal  uncertainty
>  Periods covered        second line : Weighted RMS agreement with Bulletin B
> -----------------------------------------------------------------------------
>                                x     y    UT1   LOD   dX    dY   Data Number		
> 
> VLBI Standards
> 
> BKG       
> bkg00014.eops                 62    71     3     -    14    36       4
> 58914.27 to 58935.27         109   106     4     -    40    50
> 
> GSFC      
> gsf2019d.eoxy                 37    36     2     5    11    28       9
> 58911.21 to 58939.21          79    47     4    16    50    67
> 
> IAA       
> iaa2007a.eops                 38    43     2     -    11    30       9
> 58911.21 to 58939.21         203   189    10     -    68    85
> 
> USNO      
> usn2020a.eoxy                 31    32     1     -    12    33       9
> 58911.21 to 58939.21          96    48     4     -    60    81
> 
> IVS      *
> ivs14r1X.eops                 30    25     1     -     7    20       9
> 58911.20 to 58939.22          43    46     2     -     4     9
> 
> 
> VLBI Intensive
> 
> GSI      *
> gsiint2c.eopi                  -     -     8     -     -     -       7
> 58915.33 to 58937.33           -     -    30     -     -     -
> 
> BKG      *
> bkgint14.eopi                  -     -    15     -     -     -      29
> 58910.79 to 58939.79           -     -    25     -     -     -
> 
> GSFC     *
> gsf2019d.eopi                  -     -    13     -     -     -      38
> 58910.31 to 58939.79           -     -    38     -     -     -
> 
> IAA      *
> iaa2019a.eopi                  -     -    13     -     -     -      38
> 58910.31 to 58939.79           -     -    32     -     -     -
> 
> USNO     *
> usnouint.data                  -     -    14     -     -     -      33
> 58910.31 to 58939.79           -     -    35     -     -     -
> 
> 
> GPS
> 
> CODE      
> COD*ERP_R                      5     5     -     1     -     -      30
> 58910.50 to 58939.50          51    31     -    10     -     -
> 
> JPL       
> jpl*.erp                       9    10     -     8     -     -      30
> 58910.50 to 58939.50          60    39     -    17     -     -
> 
> GFZ       
> gfz*.erp                       4     4     -     1     -     -      30
> 58910.50 to 58939.50          54    43     -    13     -     -
> 
> ESOC      
> esa*.erp                       7     9     -     4     -     -      30
> 58910.50 to 58939.50          52    32     -    11     -     -
> 
> SIO       
> sio*.erp  siu*.erp            38    47     -    17     -     -      30
> 58910.50 to 58939.50          62    49     -    19     -     -
> 
> EMR       
> emr*.erp                       3     3     -     1     -     -      30
> 58910.50 to 58939.50          55    49     -    13     -     -
> 
> IAA       
> gnss.res                       0     0     -     0     -     -      30
> 58910.50 to 58939.50          66    63     -    30     -     -
> 
> GRGS      
> grg*.erp                      58    58     -     0     -     -      24
> 58916.50 to 58939.50          57    35     -     9     -     -
> 
> ASI       
> asi*.erp                       9     9     -     0     -     -      29
> 58910.50 to 58939.50          97    43     -    36     -     -
> 
> MIT       
> mit*.erp                      12    12     -     1     -     -      30
> 58910.50 to 58939.50          58    37     -    16     -     -
> 
> IGR      *
> igs96p02.erp                  14    13     -     2     -     -      30
> 58910.50 to 58939.50          46    32     -    13     -     -
> 
> IGS      *
> igs00p03.erp                   3     3     -     0     -     -      30
> 58910.50 to 58939.50          55    34     -    14     -     -
> 
> 
> SLR
> 
> MCC       
> tg*.02                       173   234     -    29     -     -      20
> 58910.00 to 58929.00          97   161     -   124     -     -
> 
> IAA       
> slr_v.dat                     67    91     -     5     -     -      28
> 58910.00 to 58940.00         293   289     -    37     -     -
> 
> ASI       
> slr_oca*.eop                  66    97     -    20     -     -      30
> 58910.50 to 58939.50         160   281     -    67     -     -
> 
> ILRS     *
> ilrsa.eop                     43    59     -     8     -     -      30
> 58910.50 to 58939.50         214   265     -    24     -     -
> 
> 
> BULLETIN A
> 
> NEOS      
> mark3.out                     31    27     4     -     -     -      31
> 58910.00 to 58940.00          71    36    18     -     -     -
> 
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