Specifications

Doc Number: VIS-ANA-VER-01001-9002
Date: 27 May 2004
Issue: 5.0
Page: 30 of 80
Author: J. Delgadillo
Controls Preliminary Design Report Issue 5.doc
4.2.4.10 Altitude Imbalance
Since the Altitude axis has direct drive (no gearing between motors and axis) torquer motors,
the Altitude axis is very susceptible to imbalance, a potential risk for personnel and/or
hardware damage. In order to mitigate the risk, the following design has been implemented
on the VISTA Mount Control System:
1. Stow cradles will be slotted to allow for a manual altitude imbalance check.
When the Alt axis is stowed, the Alt axis manual brake release button can be
actuated and a mechanical verification of the axis imbalance can be achieved.
2. An M2 Unit Not Installed switch will detect when the M2 mirror has been
removed. If the M2 mirror if not present, the Alt axis will be Interlocked.
3. A Cassegrain Rotator Instrument not Installed switch will detect when the
CASS has been removed resulting in the Interlocking of the Altitude axis.
4. An Optical Support Structure (OSS) switch will detect when the OSS has been
removed. In this condition, the Altitude axis will be Interlocked.
The M1 Mirror Support system implements a scheme where the M1 Mirror is restrained
when the ALT axis is below 20 degrees. For redundancy, two separate switches monitor the
position of the ALT axis. If it is detected that the ALT axis is below 20° and the restraining
system hasn’t clamped the M1 Mirror, the Altitude axis is Interlocked.
4.2.4.11 AZ/ALT PDU EMC Treatments
The following AZ/ALT PDU design features will ensure that the discussed EU EMC
standards are met:
Properly Shielded Conductive Gasketed Cabinets
Completely Connectorized PDU Enclosure
EMI/RFI Connector Bachshells
Properly terminated Shielded Cables
Motor Lead Ferrite Filters
1φ and 3φ EMI Filters