Location
Cocoa Beach, FL
Start Date
7-3-1966 8:00 AM
Description
The optimum small scientific satellite system is assumed to be one in which the experimenter designs his sensor to measure the phenomena of interest, mounts it on a spacecraft, and receives a "perfect" master data tape from the ground station in return. Thus much of the experimenter's burden of the electronics design and testing now required on the spacecraft would be eliminated.
Although this optimum concept may never be attained, the purpose of this paper is to show how-over the past 5 years-an attempt to approach it has been made: The PFM encoding system has been expanded to encompass more spacecraft electronics in a central package and to incorporate hardware so that much of the time correction and error detection can be done by computer programming on the ground.
The "functional complexity" of the encoding system is shown to have increased by a factor of 20 from Explorer XII (designed in I960) to IMP F (designed in 1965); yet the volume has remained about the same, and low power (about 1. 2 watts) has been maintained. The Explorer XII encoder took about 200 transistors, and IMP F (Super IMP) would take about 4000 if conventional circuits were used. The circuit design approaches taken in Super IMP are analyzed; and the use of a completely different approach, using MOSFET blocks, is discussed. This approach has resulted in an impressive decrease in electrical parts count and an even more impressive decrease in the "dangerous" nonresistor parts count.
Evolution of Satellite PFM Encoding Systems From 1960 to 1965
Cocoa Beach, FL
The optimum small scientific satellite system is assumed to be one in which the experimenter designs his sensor to measure the phenomena of interest, mounts it on a spacecraft, and receives a "perfect" master data tape from the ground station in return. Thus much of the experimenter's burden of the electronics design and testing now required on the spacecraft would be eliminated.
Although this optimum concept may never be attained, the purpose of this paper is to show how-over the past 5 years-an attempt to approach it has been made: The PFM encoding system has been expanded to encompass more spacecraft electronics in a central package and to incorporate hardware so that much of the time correction and error detection can be done by computer programming on the ground.
The "functional complexity" of the encoding system is shown to have increased by a factor of 20 from Explorer XII (designed in I960) to IMP F (designed in 1965); yet the volume has remained about the same, and low power (about 1. 2 watts) has been maintained. The Explorer XII encoder took about 200 transistors, and IMP F (Super IMP) would take about 4000 if conventional circuits were used. The circuit design approaches taken in Super IMP are analyzed; and the use of a completely different approach, using MOSFET blocks, is discussed. This approach has resulted in an impressive decrease in electrical parts count and an even more impressive decrease in the "dangerous" nonresistor parts count.
