MPA: Meridian Photometer Array



There is an eastern line close to the 335° EDFL meridian, with three instruments located at Rankin Inlet, Gillam and Pinawa and a single station to the west close to the 312° EDFL meridian at Fort Smith. The coordinates are as follows.

            Location       Mnemonic   Lat    Long       Lat    Long
                                       Geodetic           EDFL¹
            Pinawa         PINA      50.15  264.12     58.48  334.19
            Gillam         GILL      56.37  265.40     64.54  335.14
            Rankin Inlet   RANK      62.82  267.92     70.94  337.80
            Fort Smith     FSMI      60.00  248.12     66.96  311.69

¹ EDFL - Eccentric Dipole Field Line coordinates based on the MAGSAT MGST6/80 field model for 1984.0 (?).

Platform Type and Numbers. Each message transmitted by a Canopus Platform/Instrument contains a site identification code, the Platform Type (ASCII 'P' for the MPA) and Platform Number, a single ASCII character unique to each site. These codes are as follows.


Selection Criteria for MPA Azimuths. 20 July, 1987 (Revised from a document dated 07/01/86 giving details on the East Line)

The azimuths for the MPA photometers are chosen as follows (MPA Science Team Meeting, 21 October 1983):

* The azimuth for the central site is taken as the mean of the azimuths which the Northern and the Southern sites subtend at the central site.

* The EDFL latitudes of the midpoints between the sites are computed by taking the mean of the latitudes of the corresponding sites. These are adjusted to the centre of the nearest latitude bin (Latitude bins are centered on the whole and half degree EDFL).

* The EDFL coordinates are then computed for points at 110 km altitude at elevation angles from 0° to 90° in 1° steps in the plane through the central site (using the azimuth determined previously), together with the lookangles for these points from the appropriate site. The azimuth of the midpoints from the the Northern and Southern site are then determined by interpolation at the midpoints. This fixes the azimuths of the other two sites and EDFL coordinates are computed in the same manner. These coordinates form the basis for the computation of the instrument step tables. A second set is generated for the red line, using an altitude of 230 km. For the East line

        Geodetic Coordinates
                Rankin Inlet    62.82444 N,     267.88528 E,     19 m
                Gillam          56.37611 N,     265.35833 E     145 m
                Pinawa          50.19861 N,     263.95972 E     275 m

        Azimuth  of Rankin from Gillam           10.15°
        Azimuth  of Pinawa from Gillam          188.29°

        Mean Azimuth = Gillam MPA Azimuth         9.22°   (Use 9.20°)

        EDFL Coordinates
                Rankin          70.38,          338.92
                Gillam          63.88,          336.20
                Pinawa          57.73,          335.08

        Midpoints               67.17           Choose  67.00
                                60.85                   61.00

        Azimuth/Elevation of the 110 km points
        From Rankin             193.17°/12.66°
        From Pinawa               6.32°/13.56°

For the West line.

        Geodetic Coordinates
                Contwoyto       65.75444 N,     248.74667 E,    483 m
                Fort Smith      60.01667 N,     248.04972 E,    201 m
                Meanook         54.61667 N,     246.66667 E,    610 m

        Azimuth  of Contwoyto from Fort Smith             2.87°

        Azimuth  of Meanook from Fort Smith             188.47°
        Mean Azimuth = Fort Smith MPA Azimuth     5.67°   (Use 5.70°)

        EDFL Coordinates
                Contwoyto       72.40,          311.27
                Fort Smith      66.55,          313.19
                Meanook         60.99,          313.29

        Midpoints               69.47           Choose  69.50
                                63.77                   63.50

        Azimuth/Elevation of the 110 km points
        From Contwoyto          180.86°/16.57°
        From Meanook             11.18°/21.99°

Summary of azimuths for the all sites. Also shown is the direction of the magnetic zenith, calculated as the lookangle of the 110 km point on the field line through the observer. This differs by up to about 0.25 degree from the local (110 km) inclination and declination.

        Rankin Inlet    3.2°            Mag Z   173.1°/84.6°
        Gillam          9.2°            Mag Z   182.5°/80.9°

        Pinawa          6.3°            Mag Z   185.4°/76.5°

        Contwoyto       0.9°            Mag Z   209.0°/84.2°
        Fort Smith      5.7°            Mag Z   202.7°/80.8°

        Meanook        11.2°            Mag Z   200.6°/76.9°

Field models used : Canopus EDFL Model for 1985, GSFC-980 1980.0 for 1985


| ©2005 NORSTAR