[last updated 03 April 2002]

The idea of "fiducial clock" stations was originally developed a couple
of years ago as a way to ensure that enough station clocks would be in
common among the ACs to permit a meaningful combined solution.  ACs were
encouraged to include as many fiducial sites as possible.  The list
included mainly sites from the reference frame set which have stable
frequency standards.  In addition, suitable IGS sites at timing labs were
included to prepare for eventual linkage of the IGS clock results to TAI/UTC.


PRIMARY FIDUCIAL CLOCK STATIONS

  These consist of all IGS stations located at BIPM timing laboratories
  and all other IGS stations equipped with H-masers.  ACs are encouraged
  to include as many of these as possible in their main network solutions
  or in their clock densification products.  In addition, ACs are urged to
  use a stable H-maser station as their fixed clock reference.

  Currently, the IGS stations located at timing labs (18) are:

  AMC2 (H-maser),  BOR1 (Cs),       BRUS (H-maser),  KGN0 (Cs),
  MDVO (H-maser),  MIZU (Cs),       NPLD (H-maser),  NRC1 (H-maser),
  OBE2 (Rb),       OPMT (H-maser),  PENC (Rb),       PTBB (H-maser),
  SFER (Cs),       SPT0 (Cs),       TLSE (Cs),       TWTF (Cs),
  USNO/USN1 (H-maser),              WTZA/WTZR (H-maser)

  Currently, all other IGS stations equipped with H-masers (26) are:

  ALBH,    ALGO,    CRO1,    DRAO,    FAIR,    FORT,    GODE,
  GOL2,    HOB2,    IRKT,    KOKB,    MAD2,    MATE,    MEDI,
  METS,    NLIB,    NOT1,    NYA1/NYAL,        ONSA,    PIE1,
  TID1/TID2/TIDB,   USUD,    WES2,    WSRT,    YEBE,    YELL


SECONDARY FIDUCIAL CLOCK STATIONS

  These consist of all other IGS stations which use an external frequency
  standard, either a Cesium or Rubidium clock.  ACs are asked to consider
  including as many of these as possible in their clock products.

  Currently, all other IGS stations equipped with Cs clocks (20) are:

  BAHR,    BJFS,    CHUR,    DAEJ,    KERG,    KIRU,    KOUR,
  MAS1,    MDO1,    PERT,    PRDS,    STJO,    STR1,    SUWN,
  SYOG,    TSKB,    VILL,    WUHN,    YAKT,    YAR1

  Currently, all other IGS stations equipped with Rb clocks (14) are:

  AREQ,    GRAZ,    HERS,    HOLB,    JOZE,    JPLM,    LAMA,
  MCM4,    SCH2,    TAIW,    TROM,    WHIT,    WILL,    YAR2