DX ASM in Cold Weather Update – Jan 21, 2025

Work was done in summer shutdown 2024 to attempt to address the issues causing the failures in cold temperatures with the DX ASM.  Unfortunately, we have continued to see the failures as we resume operations in cold temperatures.

If the ICS (Instrument cooling System) temperature drops below -7 Celsius (nominally chamber temperature dropping below -5 Celsius, unless the ICS offset is adjusted), the AO operation should be suspended until the ICS temperature rises above -5 Celsius (nominally chamber temperature rising above -3 Celsius)

Changes to the instrument cooling setpoint can impact seeing limited and other instrument operations and is done with care.  Users with AO programs are encouraged to coordinate their scheduled AO observations with LBTO.

DX in Cold Weather – Update (Jan 6 2024)

The failure is linked to the cooling temperature at the adaptive secondary.  The cooling setpoint was slightly adjusted to provide additional leeway while maintaining the safety of the adsec and neighboring systems.

For the safety of the system, DX AO operations should be halted if the chamber temperatures fall below -6C.

Nov 27, 2023 – DX in Cold Weather

Last February we experienced a number of failures of the DX AO at cold temperatures.  At temperatures below -5C, there has been a high frequency of communication failures.  The main signature of these failures is that the FastDiagnostics data stop being received by the DX ASM control computer. The result of this interruption is that the control computer forces a DISABLE_COIL which rests the shell and stops DX AO operation.  The issue causing this particular failure remains unresolved at this time, and for the safety of the system operational restrictions have been put in place.

For the safety of the system, DX AO operations should be halted if the chamber temperatures fall below -5C.

The team continues to review data to investigate the precise temperature threshold of these events, as well as if other environmental or operational factors (such as loop frequency) may play a role.  An off-telescope intervention will likely be required to fully resolve this.