International Laser Ranging Service

ILRS Networks and Engineering Standing Committee (NESC) Charter

1. Introduction

SLR systems constituting the ILRS provide ranging data to satellites (artificial or otherwise) to meet the requirements of the scientific community. SLR must consistently produce high quality data if it is to fulfill its potential role as a "geodetic calibrator". The diversity in hardware, software and technologies in the ground based SLR/LLR systems which make up the global network creates a unique set of monitoring problems for SLR as compared to other space based geodetic techniques. This diversity makes it necessary to establish an international entity dedicated to monitoring overall network performance and ensuring the quality and timeliness of the data it produces.

An increasing number of satellites are being launched with an expectation of SLR support. Adequate coordination between the analysis community and the network is essential to ensuring that mission needs and scientific/engineering goals are being met. Feedback from the data analysts on faulty or inconsistent station performance must be documented and corrective actions initiated as rapidly as possible. The need often exists to review network performance versus mission requirements on a periodic basis to ensure adequacy of the global SLR dataset for the full complement of approved missions.

Individual station capabilities often dictate data quality and quantity and the number of spacecraft that it can support. At present, data quality (i.e. precision, accuracy and stability) can vary by as much as an order of magnitude from one station to the next. Such a large disparity compromises the full potential of the SLR technique and requires a coordinated approach to achieve greater uniformity and versatility. A globally coordinated WG, which understands both the user needs and station constraints, can provide a broad perspective in arriving at an optimal approach.

2. Role of the Networks and Engineering Standing Committee

The Networks and Engineering SC will seek to improve and optimize the input-output functions and products of the SLR network by working closely with the data analysis community and the individual SLR stations through appropriate interactions and feedback. The primary responsibility of the Networks and Engineering SC is to facilitate the generation, collection and distribution of data in a timely and efficient manner to the user community while meeting the data quality and quantity requirements of the approved missions and to serve as a catalyst in improving the overall performance of the global network. To this end, the SC:

2.1 Provides a communications link between the analysis community and the global network

Feedback from the analysis community on network performance will be routinely sought by the Networks and Engineering SC and communicated to individual stations or subnetworks.

2.2 Facilitates ranging data problem and/or anomaly resolution

The Networks and Engineering SC will serve as a technical resource to individual stations or subnetworks in the resolution of data problems or engineering anomalies as reported by the Analysis community. The Networks and Engineering Standing Committee will routinely provide engineering feedback as well as technical information and advise and will coordinate corrective actions as necessary.

2.3 Reviews and maintains the system configuration data base

The Networks and Engineering Standing Committee will collect and maintain a comprehensive and up-to-date SLR system configuration database for each SLR station. These databases will reside, at a minimum, at the global Data Centers. Such a database is extremely useful in mission planning and network scheduling. Analysts often consult the engineering database to explain data anomalies in both short term and long term solutions so it is important that configuration histories of inactive stations be retained in the database as well. The SC will periodically query the global community of active stations to ensure that the engineering information in the database remains current.

2.4 Maintains a "knowledge base" of SLR technology, algorithms, processes, problems and resolutions

The Networks and Engineering SC will seek to share the accumulated wisdom and knowledge of the global SLR community by establishing and maintaining, at the Data Centers, an online technology database of publications and reports describing all aspects of SLR technology including transmitters, detectors, range receivers, epoch timers, satellite array designs and performance, tracking mounts, past problems and resolutions, etc.

2.5 Performs engineering analyses in support of new missions and network scheduling

The SC will assist the Mission and Analysis Standing Committees in defining the minimum and optimum network configurations necessary to support new and existing missions. Examples of engineering analysis performed by the SC will include spacecraft link calculations, projected data quality and quantity, etc.

2.6 Coordinate and catalyze engineering improvements within the global SLR network

Continued technology enhancement within the SLR community to improve the data quality and productivity is extremely important to the long-term relevance of the technique. The Networks and Engineering SC will play a pro-active role for improved performance of the network by championing new technology and engineering improvements.