Resolution of the COBE Earth sensor anomaly

Since its launch on November 18, 1989, the Earth sensors on the Cosmic Background Explorer (COBE) have shown much greater noise than expected. The problem was traced to an error in Earth horizon acquisition-of-signal (AOS) times. Due to this error, the AOS timing correction was ignored, causing Earth sensor split-to-index (SI) angles to be incorrectly time-tagged to minor frame synchronization times. Resulting Earth sensor residuals, based on gyro-propagated fine attitude solutions, were as large as plus or minus 0.45 deg (much greater than plus or minus 0.10 deg from scanner specifications (Reference 1)). Also, discontinuities in single-frame coarse attitude pitch and roll angles (as large as 0.80 and 0.30 deg, respectively) were noted several times during each orbit. However, over the course of the mission, each Earth sensor was observed to independently and unexpectedly reset and then reactivate into a new configuration. Although the telemetered AOS timing corrections are still in error, a procedure has been developed to approximate and apply these corrections. This paper describes the approach, analysis, and results of approximating and applying AOS timing adjustments to correct Earth scanner data. Furthermore, due to the continuing degradation of COBE's gyroscopes, gyro-propagated fine attitude solutions may soon become unavailable, requiring an alternative method for attitude determination. By correcting Earth scanner AOS telemetry, as described in this paper, more accurate single-frame attitude solutions are obtained. All aforementioned pitch and roll discontinuities are removed. When proper AOS corrections are applied, the standard deviation of pitch residuals between coarse attitude and gyro-propagated fine attitude solutions decrease by a factor of 3. Also, the overall standard deviation of SI residuals from fine attitude solutions decrease by a factor of 4 (meeting sensor specifications) when AOS corrections are applied

The Media and National Security

In our discussion of the media and national security, we begin with the First Amendment, not only with its legal doctrines and principles, but also with the values of the First Amendment and its function in a free and democratic society. We will first discuss how the First Amendment protects the media with respect to its disclosure of information purportedly affecting national security. We will then discuss the process by which the media voluntarily refuses to publish information on the ground that the disclosure of the information will seriously harm the national security. We will finally discuss the relationship between the government and the media with respect to obtaining information that may affect the national security

Constitutional Law Casebooks: A View From the Podium

A Review of Constitutional Law: Cases and Materials by Edward L. Barrett, and Constitutional Law: Principles and Policy by Jerome A. Barron and C. Thomas Dienes, and The Process of Constitutional Decisionmaking by Paul Brest, and Constitutional Law--Cases ad Other Problems by Paul A. Freund, Arthur F. Sutherland, Mark DeWolf Howe and Ernest J. Brown, and Constitutional Law: Cases and Materials by Gerald Gunther, and Constitutional Law: Case and Materials b Paul Kauper and Francis Beytagh, and Constitutional Law: Cases--Comments--Questions by William B. Lockhart, Yale Kamisar, and Jesse H. Choper