When it comes to collecting and interpreting a multitude of satellite orbit observations from numerous observations throughout the world, there are at least three impediments: diverse observation standards and calibrations, competition and secrecy, and differences in orbit determination schemes.
Orbit element sets are far removed from the observations. They obscure uncertainties and employ unspecified orbit determination models. Elements from all sources cannot be combined into coherent projections of positions of satellites in the future. Collaboration must begin with well-characterized observations that include calibrations and sources of imprecision. Some sources of observation seek not to disclose the quality of their observations — either to protect national security or just to avoid embarrassment. Some do not use the actual observations for estimating orbits. They use convenient times along the locally developed track of the observing instrument, which diminishes the quality of the orbit estimates at the outset. One expects, but cannot rely on, consistency at least for orbits determined from a single source. Apart from geostationary orbits, no single source can capture sufficient observations of more than a few satellites. Proliferation of commercial observations creates competitive pressures and sometimes quality claims that cannot be verified. Commercial sources would rather provide element sets than observations. Some satellite operations wish to cloud where their satellites are to mask their existence. These are just a few impediments to productive collaboration.
These types of impediments have almost all been overcome in other disciplines, particularly weather forecasting and climatology. In the 1950s, the American Meteorological Society began certifying weather forecasters who passed a rigorous set of tests and demonstrated forecasting proficiency. There were many reasons for universal collaboration despite international friction. Today’s weather in one place might be tomorrow’s weather someplace else. Fairly frequently, widespread observations were necessary in order to create and improve models. In 1961, President Kennedy proposed “cooperative efforts between all nations in weather prediction.” The International Meteorological Organization became the World Meteorological Organization (WMO) under the UN. The goal was more than knitting national systems together. The WMO was to develop a Global Observation System, a Global Data Processing System, and a Global Telecommunications System. Just what we need for Space Situational Awareness (SSA). As with all UN activities, only peaceful efforts are allowed.
Weather collaboration developed expeditiously. It will evolve continuously. Norway introduced the scientific method to global mysteries, testing hypotheses with observations. The WMO’s Regional Basic Synoptic Network broadcasts worldwide the observations of more than 4,000 instruments all over the Earth. It is a paradigm for satellite observations.
From the outset in the 1960s, the WMO sought an integrated system of observations, communications, and analysis. It developed two categories of models: experimental and operational.
Operational models are used for local estimation. In our parlance, these are used by satellite owner/operators, but they are not necessarily accepted at face value. They are moderated by those who locally know best the characteristics of their areas. The European Centre for Medium-Range Weather Forecasts (ECMWF) in the United Kingdom, is the center of activity and excellence. Two supercomputers, maintained at the state of the art with biennial upgrades, assimilate millions of observations from everywhere, discriminate good from bad and those that add value from those that do not with consensus criteria approved and transmit products in two directions: 50% for research, and 50% for operational use. The Centre is staffed by experts from member nations assigned for a few years, then to return to their home services. The Centre must deal continuously with language, standards, and societal issues. But a multitude of observations increases complexity and cost. The most prescient in the ECMWF discerned that predictions can never be perfect. They seek “more accuracy with less precision.” Most important, there are objective local and central experts, exceptionally familiar with data, models, products, and relevant conditions examining predictions and rejecting those that are unjustifiably divergent. Operators can use their own estimates rather than the central product, if they can justify rejecting the central estimates and distribute their preference to all, who can make similar judgments.
Resolution 40 of the WMO is a template for the orbit estimation community, mandating for all members free and unrestricted essential data and worldwide cooperation in establishing observation networks for peaceful purposes. It has survived wars and rivalries because the product is essential to everyone. Not joining puts outliers at risk of flying blind. The WMO is redefining itself to work in a mode of private platforms and private networks, both a technical and a diplomatic challenge.
Proliferation of isolated observation and estimation capabilities is expensive, inefficient, and ineffective. No single isolated entity can acquire or assimilate sufficient data or computational resources for accurate, precise, and uniformly understood orbit estimation. Effective collision avoidance is impossible without this.
Overcoming the diplomatic, political, and technical difficulties is well worth the effort. The World Meteorological Organization succeeds. It must be consulted, and its practices applied to sustaining the space environment.
David Finkleman was chief technical officer of U.S. Space Command and NORAD for nearly 20 years. He is a lifetime fellow of AIAA, AAS, AAAS, IAASS, and other professional organizations, a permanent academician of the International Academy of Astronautics and the International Institute for Space Law, and a retired U.S. Air Force colonel. He earned a Ph.D. in aeronautics and astronautics at MIT and was associate professor of aeronautics at the U.S. Air Force Academy.
This article originally appeared in the October 2021 issue of SpaceNews magazine.