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The consecutive failures of the geosynchronous Anik‐E1 communication satellite on January 20, 1994, and Anik‐E2 about nine hours later on January 21 (both incidents occurred on January 20 local time) received considerable publicity because the malfunctions of the satellites disrupted television and computer data transmissions across Canada, as well as telephone services to remote northern communities for hours. This often‐cited event is revisited here with materials not covered before. Using publicly available information, Anik‐E failure details, media coverage, recovery effort and cost incurred are first presented. This is then followed by scrutiny of space weather conditions pertinent to the occurrences of the Anik‐E upsets. We trace the space weather episode's inception on the Sun, propagation through interplanetary medium, and manifestation in magnetic field variations as well as in energetic electron flux increases, and its eventual impact on the Anik‐Es. The genesis of the energetic electron enhancements that have been blamed for the satellite malfunctions is thus traceable via high‐speed solar wind stream with Alfven wave fluctuations to a longitudinally wide coronal hole on the Sun. Furthermore, strong magnetic pulsations preceding electron flux peaks indicate Pc5 ULF (Ultra Low Frequency) waves as a probable acceleration mechanism for the energetic electron flux enhancement that resulted in the internal charging of the Anik‐Es. The magnetic fluctuations may even be possible triggers for the subsequent discharge that caused the satellites to malfunction. This incident illustrates that satellite operators should be on alert for elevated high‐energy electron environment that is above established thresholds, as specifications in satellite design may not render a satellite immune from internal charging.

On-orbit estimation of spacecraft mass properties can be useful for planning of maneuvers and potentially for determination of spacecraft fuel load. In this paper we describe the application of a weighted-least-squares parameter estimation technique to simulated and onorbit gyro data for the purpose of determining spacecraft mass properties.

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