This paper deals with the design and development of an embedded microcontroller based Adaptive Signal Conditioning System (ASCS). The system is especially relevant to applications such as launch vehicle telemetry where the number of parameters to be acquired is large as well as their types and dynamic ranges vary over a wide band. We bring out the salient aspects of the system design by way of both the hardware and software to show how it supports adaptability of all the major signal conditioning parameters such as gain, offset and bandwidth. The test results are also brought out to establish the system functionality. Its application potential is then discussed to show the advancement that it offers for telemetry in the context of advanced Space Transportation Systems and next generation missions such as Reusable Launch Vehicles and Human Space Flight.

An Adaptive Signal Conditioning System for Launch Vehicle Telemetry Applications

This paper deals with the design and development of a Data Acquisition System (DAS) based on a multi-core sigma-delta Analog-to- Digital Converter (ADC) Application Specific Integrated Circuit (ASIC). The ASIC is indigenously designed and fabricated in Semi-Conductor Laboratory (SCL) in 180 nm CMOS process and consists of 16 independent autonomous ADC cores complete with sigma-delta modulator and digital FIR filter. A 32-channel DAS is realized using the ASIC and high density Field Programmable Gate Array (FPGA) device. The system has an output serial link compatible to launch vehicle telemetry systems. The module occupies an area of 75 mm x 75 mm only and weighs only about 150 grams for the lowest per-channel footprint and weight reported. The details of the design and functional evaluation carried out on the module are explained and the key performance metrics quantified. The test results show that the design is well suited for instrumentation application in industrial and automotive systems as well as in miniaturized avionics systems for ISRO’s future space missions such as Small Satellite Launch Vehicle (SSLV) and Re-usable Launch Vehicle (RLV) where it can contribute substantially to volume, weight and power reduction.

A Miniature Data Acquisition System using an Indigenous Sigma-Delta ADC ASIC

In this work, the salient requirements and features of the baseband telemetry system used in Reusable Launch Vehicle—Technology Demonstrator Hypersonic Experiment mission are discussed. The configuration of the overall system, subsystem components and their features are described in brief. The unique requirements of the telemetry system, when compared to that in a conventional launch vehicle, by way of a large number of temperature and strain measurements that enable the assessment of structural integrity and mission performance in re-entry mission, are dealt with, along with the system configuration to cater to these. Subsequently, two new units have been described—Strain Data Acquisition Unit and Multiplexed Data Acquisition Unit that were inducted specifically to cater to strain measurements using strain gauges and temperature measurements using thermocouples respectively. The optimized subsystem configurations for these units are described and their field performance during flight is analyzed. This work further discusses a novel method of data recovery for those measurements affected by the baseline offset shift caused by the presence of a chassis voltage and poor isolation of sensor to chassis.

Instrumentation and Baseband Telemetry for RLV-TD HEX Mission

We describe the design and development of a baseband telemetry system for multistage launch vehicles. The system is organized as a three tier one with remote data acquisition and processing units and a centralized control unit. The front-end Data Acquisition Units (DAUs) feature software programmable amplification, offset, filtering and sensor excitation and thus are flexible to interface directly to a variety of sensors used in launch vehicles. The Data Processing Units (DPUs) gather data from DAUs through a serial link compatible to RS-485 standards and carry out a variety of data analysis and data compression functions on selected channels under software control. The central Telemetry Control Unit (TCU) receives this data through a transformer isolated link compatible to MIL-1553B standards and performs the functions of data delay, data storage, onboard computer data monitoring, PCM formatting and pre-modulation signal conditioning to achieve miniaturization. The configuration and features of this telemetry system make its integration simple without compromising on data integrity and reliability and suit the adoption of futuristic technologies and concepts such as smart sensor networks, adaptability, reconfiguration and vehicle health management.

Madaswamy Pillai

Papers

A versatile, software programmable telemetry system for satellite launch vehicles