A Geomagnetic Monitoring Station is being added to the Observatory in Spring 2025 for monitoring changes in the earth's magnetic field and to supplement and build upon the Observatory's existing Aurora monitoring that use a Black/White AllSky Camera and new NorthCam Colour Camera.

During Commissioning & Diagnositics phase it was discovered that the initial setup suffered from two significant issue (Noise & Anomalous Spiking) that require remediation.

The following notes describes the Remedial Work

Other notes  :
| Review | SAM III | Site Prep | Assembly Design | Parts Assembly | Testing | Final Assembly | Installation | Commissioning | Remedial Work |

Proposed Remedial Plan (2025-05-01) - For Discussion

The propsed remediation plan to resolve issues discovered during Commissioning Phase are outlined below

- dig up existing setup (downhole assembly and cables)
- retrieve existing magnetometers and temperature sensor
- build new assembly,
    - incorporate wider separation between magnetometers
    - connected using S/FTP shielded cable,
    - cable shielding will be grounded at sensor assemby end, by connecting it a common drain wire
       that will be run out of the assembly and embedded in the side of hole  (shielding won't be grounded at the Observatory end)
    - continue to use standard method using unbalanced circuits
- relocate the Temperature Sensor into its our buried enclosure at the same depth as the magnetometers, but separated by some distance.
- install new assembly
- connect cables back to SAM unit in Observatory

Alternative Remedial Plan - For Consideration

 -dig up existing cables from hole
- retrofit TIA-422 balanced circuit system above the
   - build and install outdoor interface box at sensor end incorporating TIA-422 balanced circuit board
   - build and install circuity at SAM III end using TIA-422 balanced circuit board
   - set jumper on SAM III to 12v
   - may need to lay & use use new cabling ? (how to ground if using shielded cabling)

potential issues
 - the time to extra complexity at both outdoor and indoor ends of the cable
-  the uncertainty on whether the spikes issue will be solved or not.
- uncertainty on making the outdoor enclosure be fully water proof..

Earlier Plan (from 2025-04-18) - On Hold

It seems that the Y Axis Magnetometer is compromised in some way (but needs to be confirmed with new tests on 2025-04-26).

Rather than dig up the existing 3-axis Sensor Fixture and pull out the working X & Z sensors and repair or install a new Y Axis magnetometer  it is proposed to build a dedicated new Y axis fixture for burial beside the existing fixture.

Requires
 - new FG-3+ magnetometer (£67.70 from https://robosavvy.co.uk/fgsensors-fg-3-sensor.html)
 - new fluxgate capacitors
      10 uF, 25v Tatalum Capacitor  (£ 1 + delivery)
     100 nF, 25v Ceramic Capacitor (£ 1 +delivery)
- new piping  (3 ends caps, 1 x 90 deg bend, 1 x 135 deg bend, 2 connectors - £10)
- new 15m length of Cat6 cable required (already available, but may opt for a shielded Cat6 cable given lessons / experience.

Work
  Assembly / test new magnetometer & fixture
  Part dig existing hole, install new Y Axis fixture
  Dig up trench,  thread new cablethrough corrugated pipe (if possible) or run cable beside corrugated piper

| Review | SAM III | Site Prep | Assembly Design | Parts Assembly | Testing | Final Assembly | Installation | Commissioning | Remediation |