HP RC3000 Manual Do Utilizador
RC3000 Antenna Controller
Chapter 1
Introduction
11
1.3.5 Timekeeping
There are several versions of time (system, sidereal, referenced and GPS) discussed within this manual.
System time is maintained by the RC3000’s real time clock. The real-time clock is backed up by battery
so that system time is available as soon as the RC3000 powers up. The system time is used to calculate
sidereal time for maintaining track tables. Since satellite’s do not experience time shifts (such as from
Standard Time to Daylight Savings Time or when moving from one time zone to another), it is
recommended that system time not be modified while active track tables are present. If system time is
changed, the information stored in track tables for inclined orbit satellites will no longer be valid.
so that system time is available as soon as the RC3000 powers up. The system time is used to calculate
sidereal time for maintaining track tables. Since satellite’s do not experience time shifts (such as from
Standard Time to Daylight Savings Time or when moving from one time zone to another), it is
recommended that system time not be modified while active track tables are present. If system time is
changed, the information stored in track tables for inclined orbit satellites will no longer be valid.
The RC3000’s system time is set to approximately Universal Coordinated Time (UTC) at the factory. It
will vary from UTC due to the tolerance of the real-time clock.
will vary from UTC due to the tolerance of the real-time clock.
If the optional GPS receiver is installed, the RC3000 parses UTC from the data sent by the GPS receiver.
This data is only available when the GPS receiver is sufficiently locked on to GPS satellites to determine
UTC. The RC3000 allows the user to synchronize system time to the UTC reported by the GPS receiver.
This data is only available when the GPS receiver is sufficiently locked on to GPS satellites to determine
UTC. The RC3000 allows the user to synchronize system time to the UTC reported by the GPS receiver.
The period of a satellite’s motion is one sidereal day (approximately 23 hours 56 minutes 4 seconds).
Entries in the track table for an inclined orbit satellite are stored at intervals of 1/48th of a sidereal day.
The RC3000 determines at what point in a sidereal day (with respect to the RC3000 reference) it is by
calculating how many sidereal days have passed from January 1, 1992 until the present system time.
Entries in the track table for an inclined orbit satellite are stored at intervals of 1/48th of a sidereal day.
The RC3000 determines at what point in a sidereal day (with respect to the RC3000 reference) it is by
calculating how many sidereal days have passed from January 1, 1992 until the present system time.
In several screens the RC3000 displays a reference time. The user may designate a three letter
timezone designation and an hourly offset from system time. This allows the user to display local time or
some other reference time without modifying system time. If system time is maintained close to UTC, the
reference time displayed may be of use to operators for coordinating events.
timezone designation and an hourly offset from system time. This allows the user to display local time or
some other reference time without modifying system time. If system time is maintained close to UTC, the
reference time displayed may be of use to operators for coordinating events.
See section 3.3.2.3 for details on time maintenance.
1.3.6 Drive System
The RC3000 implements several mechanisms for the driving and monitoring of the azimuth, elevation
and polarization axis.
and polarization axis.
Position Sensing and Limits
The RC3000 senses absolute axis position using feedback from various sensors (potentiometers,
resolvers, inclinometer for elevation, etc). The sensed voltage is scaled appropriately for the particular
mount. This sensed position is displayed in angular format.
resolvers, inclinometer for elevation, etc). The sensed voltage is scaled appropriately for the particular
mount. This sensed position is displayed in angular format.
For systems requiring very small movements for inclined orbit tracking, the RC3000 also supports pulse
feedback from the azimuth and elevation axis. Sensed pulses from the axis motor don’t provide an
absolute indication of position but allow for very precise relative movements.
feedback from the azimuth and elevation axis. Sensed pulses from the axis motor don’t provide an
absolute indication of position but allow for very precise relative movements.
The boresight of the antenna is displayed for the azimuth and elevation axis. In elevation, this angle is
with respect to the local horizontal. In azimuth, this angle is with respect to the centerline of azimuth
travel.
with respect to the local horizontal. In azimuth, this angle is with respect to the centerline of azimuth
travel.
The following diagram shows a typical range of movement for mobile satellite antennas. Note that
elevation movement to the stow position is limited about a small range of azimuth movement in order to
ensure safe stowing of the antenna.
elevation movement to the stow position is limited about a small range of azimuth movement in order to
ensure safe stowing of the antenna.