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The station was cold upon arrival, had a strong smell of propane, and the emergency shut-off valve had activated. There was a 10-pound stack of ice on the exhaust shroud and a 3-inch plug of ice had formed inside the air filter. The nitrogen tank was not turned on, which left propane vapor pressure as the only force pushing fuel into the station. Propane boils (vaporizes) at -44 C, so at temperatures colder than -44 C, there was not enough pressure to push propane into AGO-6.

2) The outside temperature dropped to -48.8 C on June 17, 2000, the day the station shut down. Propane could not vaporize at this temperature, the force pushing the fuel into the station into the station dropped, and TEG starved for fuel.

3) As fuel starvation continued, burner temperature decreased to the point where the igniters turned on. The igniters placed a large load on the TEG/Turbo batteries and drained them.

4) As the TEG temperature drops, the amount of heat transfer to the freon and exhaust shroud decreases. The TEG exhaust (carbon dioxide and water vapor) passing through the cold shroud condenses and freezes, causing the ice plug.

5) The propane shut-off valve is designed to close at -20 C. As much as three days may elapse between station shut-down and the interior cooling to -20 C. During this time, propane is still being delivered to the TEG and not being burned. This would account for the strong odor of ethyl mercaptan in the shelter. The air filter and the exhaust stack, which were blocked, slowed the escape of the propane.

The technical service team easily started the TEG, used fuel left in the main tanks, and raised the station temperature to 20-25 C. That temperature was maintained throughout the service call.

AGO-6 was approximately 2 feet above the surface and the wind effects created a bowl-shaped hole about 4-5 feet under the bottom of the station. The support posts were pulled out of the ice, new footers were placed, and the AGO was raised to its maximum height. The corner guy wires were reattached at the base only. The upper guy wires were not necessary for the stabilization of the site. One complete cable set with deadmen are on the site for next season. New footers will be needed, however.

The TEG Turbo was modified to allow it to extract power directly from the PSC. The priority of the turbo was reset to the highest priority for power use at the station. New batteries for the turbo were installed. Batteries for the electronic shutoff valve were also replaced. The manifold propane pressure is set at 3.0 psi. Maximum burner temperatures that could be reached were well above 300 C, but burner temperatures were set between 295 C to 300 C. Freon pressure was maintained at 20 psi. At burner temperatures of 300 C, freon pressure is 24 psi. Aluminum baffle plates were installed above the vertical air fins to restrict air movement through the internal TEG heat exchanger.

Two Storage computers (Rev 2, SN: 00-011 and 00-012) were installed in the DCU. The old storage computers were removed and will be shipped to Augsburg College for data retrieval and processing.

All functions of the PSC were normal when it initially powered up. All channels were checked and worked effectively. After the PSC and DCU were activated, power was delivered to all experiments. The BAGOEXP board was updated with PIC TIPIC002 rev. 04. See AGO6.AGO for experiment power settings, priorities, and other station information.

All functions were normal when the unit was turned on. Non-volatile random access memory was installed in the DAU and the DAU software was upgraded to Rev. 3. See AGO1.AGO for DAU settings.

Data was examined to verify the operation and leveling of the magnetometer. The magnetometer needed re-leveling, which was done on day 346. The box containing the sensor remained in its original position and the cover for the vault was raised to the surface and marked with flags.

The electronics were checked out per the servicing documentation. The results of the initial checkout were faulty due to the magnetometer not being level. The magnetometer was leveled and the D axis was zeroed, the data collected is as follows:

The search coil experiment data showed variance in relation to data collected the previous year. The experiment receiver was examined and there was a noticeable change to the readings on the front panel when the lamp was engaged. Meter readings would not return to their original position when the lamp switch was engaged or disengaged. The unit was replaced and data was examined. Data in the new unit resembled that of the previous year. The overall system was determined to be operational and functionally sound. Sample data from the old unit was collected and stored to the laptop prior to the instrument being replaced. Data was being collected from the new unit but was unsuccessfully recorded because the team ran out of time on the pull out.

The riometer vault was partially dug out 3-4 feet this season. The 12-foot flags indicating the vault location were exposed a foot above ground, so about 8 feet of digging remains. The hole is covered and marked for continued effort next year. Additional digging equipment will be brought to excavate a hole 12-feet deep through an area crossed by cables. Sample riometer data was collected prior to the resupply flight and stored to the laptop.

1) The Riometer experiment needs an extension cable to connect the old cable to the station electronics. The old cable is stretched tight after raising the AGO.

2) Whenever a power source or experiment has been modified, it should be tested for greater than 1 MOhm isolation to chassis BEFORE the unit is connected to the PSC. The PSC is very sensitive to violations of this specification.