LIGO Document L950128-x0

LIGO Coordinate System

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Document type:
L - Letters and Memos
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Notes and Changes:

Migrated document information from the old DCC:
- Full document number: LIGO-L950128-00-U
- Author(s): Gerry Stapfer
- Document date: 1995-02-15
- Document received date: 1997-09-22
- Document entry date: 1995-02-15
8/8/2013 D. Coyne: The mid-station center of the BSC coordinate distance from the vertex (or global coordinate system origina) is quoted in this document as 2018 m. This is not correct. The correct value is 2019.001 m. The derivation is as follows: The BT/VE Interface: The Beam Tube (BT) to Vacuum Equipment (VE) interface is at the weld seam for the large gate valves. These locations are marked by brass markers (monuments) denoted BTVE-#. For example the BTVE monument for the X-mid station at LHO closest to the corner station is BTVE-6. Nominal Locations: The drawing D950021-v1(-B), "LIGO Arm Layouts" shows that the interface between the Beam Tube (BT) and the Vacuum Equipment (VE), which is the valve weld, is 46,000 + 1,961,500 = 2,007,500 mm from the vertex (global coordinate system origin). The BT sub-assembly end locations drawing (D950032-x0) also shows that the BT to VE weld interface is at 2,007,500 mm. As-built, surveyed locations: The as-built, surveyed coordinates are given, and summarized, in T980044-v1 (-10). In this document the global X-coordinate of the BTVE-6 marker is 2,007,500 mm, both by design and as surveyed, which confirms the information above. The center of the mid-station BSC chamber: The previous (iLIGO/eLIGO era) version of the vacuum equipment (VE) arrangement drawings for the mid stations (e.g. D961168-v1 for the LHO right/X mid-station) shows that the BSC chamber center was 11,501 mm from the weld interface with the beam tube (BT) contractor. So the mid-station BSC chamber center was 2,007,500 + 11,501 = 2,019,001 mm from the global origin (vertex).
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