The antenna control servo system (ACSS) is built to control a 32-mtr deep space antenna (DSN) system. The antenna axis configuration is an elevation over azimuth. AZ has steerability of  270  and EL has steerability is 0-90  .

The system consists of ACU rack, ADU rack, DBR rack and portable antenna control unit (PACU).

ACSS is an antenna pointing system, controlled manually or automatically, which positions the antenna to receive the peak signal from a satellite. This ACSS described here is designed to position an antenna in azimuth, elevation axis of movement for the purpose of location and tracking the satellite of interest.

The ACSS uses the latest processor technology, providing accurate positioning, high reliability and maximum system flexibility. The system has capabilities for rapid access with RS 232 or RS-422 remote control applications.


The function of the system is to control the antenna movement in azimuth, elevation to track satellites through various functional modes. It continuously monitors and displays axis angle, the functional mode selected, and indicates errors like limits & interlocks if any.

Application: –

The antenna control servo system (ACSS) is an intelligent and powerful control system which finds its applications on earth stationed antenna control for satellite tracking purpose in manual and advanced auto track modes.

ADU Specifications:

ADU 4-channel analog inputs ±10V from ACU for drive amplifier interface.8-channel analog outputs to ACU from drive amplifier.
Motor Interface 2 motors each for azimuth and elevation axis interface.
Front Panel interface Potentiometer for speed selection on front panel of maintenance panel, Azimuth and elevation ON / OFF switch, command interface i.e., Enable, selection switches rocker switches.
Power Supply 24V DC for drive amplifiers, motor brakes and interlocks
Display 4 analog panel meters, two each for AZ & EL axis on the maintenance panel.
Protection Circuit breakers at the input mains contactor choke and filter in series with the power supply to the drive amplifier.Fuse between Drive amplifier and Regenerative resistorCircuit Breakers at the Input of the power supply.
AC Power input 415V AC 3Ø, 50Hz, ±10% Tolerance.230V AC 1Ø, 50Hz, ±10% Tolerance.
Environmental Operating Temperature: 0 to 50  C.Storing Temperature: -20 to 70  C.RH up to 95% non-condensing.

ACU Specifications:

Bus compatibility: cPCI Based
Type of interfaces
Analog interface ±10 VDC analog output with fine setting of 1mV with analog Isolation.±10 VDC differential analog input with 16-channels interface with measurement accuracy of 0.5% of Full Range with analog isolation.
Digital Interface 64-channels optically isolated with isolation level of 1.5kV
Encoder interface 2-channels of EnDAT Encoder type of interface.
Resolver interface 2-channels of Resolver interface with accuracy of 1 arc minute
IRIG-B Interface 1-channel of IRIG-B interface of modulated signals level from 250mVp-p to 10 Vp-p. Modulated ratio of 1:2.5 to 1:6.
1-channel Ethernet interface 10 or 100 Mbps Ethernet interface and 1:4 Ethernet switch for interface with SGC, STC and SRCU.
COM port RS232 / RS422 interface to ATE
PACU interface RS422 interface for Portable ACU
Display 6” / 9” Graphical LCD.
Keyboard Membrane keyboard suitable for the application.
AC Power input 230V AC 1Ø, 50Hz, ±10% Tolerance.
Power supply SMPS based with low EMI / EMC should be used.
External interface
Hand wheels 2-channels of Incremental Encoder interface for movement of AZ and EL axis in manual mode.
PACU RS422 serial Asynchronous interface for communication with PACU.
Ethernet Hub or Switch 4-port or 1:4 channel Ethernet switch interface.
ADU Interface Analog, Digital interface with Antenna Drive Unit.
Potentiometer Interface 2-channel of 2 turn Potentiometer interface from the Encoder Boxes. The excitation for Potentiometer is 5V or 10VDC.
Tilt Sensor Interface
Wind Speed-Operational-Survival-Stowing-Precision tracking 60 Kmph160 Kmph60-90 Kmph30 Kmph gusting to 45 Kmph
Environmental Operating Temperature: 0 to 50  C.Storing Temperature: -20 to 70  C.RH up to 95% non-condensing.
Mechanical Dimensions 19”, 4U / 6U height, 400 mm to 600 mm in depth should be used.

PACU Mode:

Function : Dumb Terminal
On receiving echoes character
On key press transmits key code

Interface : Asynchronous Communication

Bus Drivers : RS-422

Baud Rate : 2400 baud to 38.4k baud

Display : Standard 20×4 displays

Keyboard : 20 keys membrane keyboard
5 x 4 matrix keyboard

EnDat Reader Mode:

Function : EnDat/SSI Reader
Upon selection stores local flash
Upon selection transmits continuous to remote system
Upon selection transmits stored data to remote system

Remote Interface : Asynchronous Communication
Bus Drivers : RS-422
Baud Rate : 2400 baud to 38.4k baud

EnDat Interface:

i. Type of Encoder : EnDat / SSI Encoder

ii. Number of channels : 1 channel.

iii. Interface : EnDat 2.2 Interface

iv. Isolation : Not Available

v. Bus Buffer : Differential (RS485 Level)

vi. Speed : Up to 4 Mbps (Programmable)

vii. Data Length : Programmable

EnDat Angle Update Rate : 200Hz Max

Ext/Int Trigger : Default Internal triggering at fixed update rate 200Hz is selected
Upon selection EnDat Angle update is possible on Ext triggering

Ext Trigger signal : TTL, Positive Edge

Trigger out : TTL

Sampling delay from ext trig : 10uSec Max