Information Systems Standards Open New OpportunitiesM. L. MacMedan
In the early days of the space program and for many years thereafter, JPL's missions were characterized by goals of perfection, optimization, and reliability. Cost was a factor, but often took a back seat. Today, we work under the guidance of "Faster, Better, Cheaper." No longer can we take the time or spend the money to customize routine operations for each mission. That is where standards come in.
The objective of the Information Systems Standards Program is to develop "leading" standards to guide future designs in areas of common and routine operations, so that proportionally less money can be expended on the functions common to all missions, leaving more money for the mission's nonroutine and unique needs.
"Leading" means the standards do not necessarily document what has been done before, but are well-engineered pathways to guide future end-to-end system designs to converge on a common way of doing the routine things that each spacecraft, tracking station, and ground processor do. Since no two missions are exactly the same, to apply a single standard over many missions requires it to have a certain flexibility to accommodate needed variations. On the other hand, this flexibility must necessarily be limited if we hope to control costs. Thus the standards represent a delicate balance between achieving functions that are "good enough" and at "reasonable cost" not for a single mission, but over the majority of them. As can be imagined, it is difficult to easily quantify such tradeoffs, especially with ill-defined future needs, and so good engineering judgment and vision are paramount to the success of a standard.
The importance of having well-engineered, leading standards to help make our missions more operable was emphasized by NASA when JPL was recently named the Lead Center for the NASA Space Mission Operations Standardization Program.
Leading standards must be based on the latest (or even not-yet-quite-available) technologies, because they will be used to guide designs of future missions. Technology having widespread applicability for future missions is always a candidate for a new or revised standard; is is not the intent of our standards program to unnecessarily lock in old techniques or stifle new ones. Therefore, there is a close relationship between the standards and the technology programs at both Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL).
This relationship has been particularly successful in the area of packet telemetry where the standard has made feasible:
Other technology collaborations are channel coding, which is necessary to provide the nearly-error-free channel made necessary by compression, and the data-driven feature of packet telemetry; and data compression itself. Current collaborative work involves Turbo Codes, new techniques for Frame Synchronization, and development of a data set transfer protocol useful for assuring complete, error-free, end-to-end delivery in the long-time-delay environment of deep space.
Often, proposals for new missions are offered to the National Aeronautics and Space Administration (NASA) on the premise that the data system "will not be changed from the last project," thus saving lots of money. In actuality, this has never happened. In the end, some redesign has always been necessary, because the point designs we have used in the past to optimize the data system for a particular mission have no flexibility to accommodate even the limited changes necessary to work with a different project. These standards do allow for a range of flexibility to accommodate not all, but a majority of new missions.
Rather than develop standards in isolation just for JPL, with its small market, our approach for the last 15 years has been to work these problems in the international forum of the Consultative Committee for Space Data Systems (CCSDS). The CCSDS is composed of some 30 space agencies of the world, all with similar problems to ours, and has collaboratively produced over 20 different Recommendations (Blue Books). Having engineers from several different agencies working on a solution leverages our contributions to get a superior engineered result. While this international approach helps industry by enlarging the market for standard products and solutions, it also enhances the ability of (the Telecommunications and Mission Operations Directorate (TMOD) to service its many foreign customers (~50%). CCSDS has also been found beneficial to NASA by providing a neutral, third-party umbrella under which NASA centers find it easier to cooperate. (It neutralizes the inter-center "not invented here" syndrome.) Furthermore, in the last two years, a cooperative effort among NASA, the National Oceanic and Atmospheric Administratoion (NOAA), and and the Department of Defense (DOD) has been formed to respond to the White House thrust to establish commonality among all government space operations. This has the potential to enlarge the vendor market for standardized products and make more of them available cheaply and quickly ("off the shelf "), particularly if (as is already happening) this thrust is carried into CCSDS.
Technical Areas Standardized
There are three major technical areas in which the Information Systems Standards are concerned: Space Communications (which moves the data without its interpretation); Information Interchange (which deals with the interpretation of the data content but not its transport); and provisioning of Mission Services for routine operations such as data delivery, scheduling, and tracking operations.
Space Communications Standards
These standards use a layered approach to communication protocols that have been adapted or developed for space use. It includes the physical layer (RF and Modulation) where important work has been done to establish a common link design control table; a program for optimizing modulation indices for simultaneous telemetry, command, and ranging; and development of filtering techniques for reducing the occupied bandwidth of emissions by as much as 10 times. It includes data link layer protocols (error correction coding, framing, randomization, and synchronization), and a rudimentary network layer (Packetization). Current work includes developing a new standard for Turbo Coding that will improve the link quality in very-low-SNR environments. This is needed because advanced data systems operate in a data-driven mode where errors are simply not acceptable.
Other work, being developed jointly with DOD, uses these lower layer protocols on which to build an upper layer set to provide end-to-end reliable communications using Transport, Security, and File Transfer protocols. These layers are based on the corresponding traditional internet protocols, modified as necessary for the space environment.
A standard for lossless data compression that uses source encoding has been developed that will improve the throughput of the space link without propagating errors in the end user's data reconstruction process. A time code standard has also been developed, which reduced to four the proliferation of 53 different time codes that were used by JPL missions in the past.
Information Interchange Standards
This area is developing standards and tools for improving the interpretation of space data in a permanent way; useful during a project and after it has ended, when its knowledgeable people are gone. Included are standards for formatting space data sets, languages and formats for describing the formats of the data sets, and dictionaries for describing the contents of the data sets (e.g., measurement names, units, DN-to-EU conversions, etc.) In addition, a distributed, hierarchical system for registering the languages, formats, and dictionaries with a control authority has been set up in NASA and several other agencies, and a network linking these control authorities to freely access the distributed data base is being developed. A toolkit for working with the Standard Formatted Data Units is also available. Current work includes developing Archiving Standards for space data.
With the new NASA Space Operations contract coming soon, it is important to define the standard services that NASA will provide its customers. Today, nearly each customer negotiates a different and uniquely defined set of services to receive from NASA, because there are no standards. These deal with the delivery of Telemetry data, handling of Telecommand data, scheduling, tracking and orbit determination, time correlation, and so on.
TMOD is becoming a provider of standard operational services to reduce the costs of doing business (up to now, providing customized solutions) with our customers. To be able to provide these common services requires the establishment of certain standards for the operation of space and ground data systems. The establishment of these standards for routine operations will enhance interoperability among mission operations, ground support services, and agencies, and encourages product competition from smaller manufacturers, and lowered costs when operations are outsourced.
The secret of a well-engineered service standard is to allow needed flexibility to serve the majority of customers while limits are put on the customization (or variety) of services to constrain costs. To the extent possible, these services rely on the underlying features of the existing CCSDS Recommendations (such as Packet Telemetry, Telemetry Channel Coding, and Standard Formatted Data Units) for handling and accountability. Standard Services are being developed locally at JPL by TMOD Level-0 System Engineering, and the standards program is linking this work to other NASA centers and space agencies through the CCSDS.
The first standard Service definitions are nearly ready: Return-All-Frames Service for telemetry, and CLTU Service for telecommand. Others will follow soon, and as more agencies and projects adopt these standards, it becomes easier to interface with agencies, NASA centers, and projects.
At JPL, the standards program also promotes the notion of Application Engineering, which we view as a help to the first-time implementor of the standard to interpret and apply it properly. Our CCSDS experts are available to answer questions and to provide background information on the program, on the standard itself, or possibly to help with identification and selection of conforming CCSDS products on the market.
In addition, periodic "Industry Days" are held for U.S. industry to keep it abreast of the latest developments in the program, and for the program to learn what new standards are wanted by industry.