Equatorial Ionospheric Scintillation Flight Testing.
Abstract
A series of airborne measurements were made during the fall of 1971 in the western Pacific area. The 250 MHz beacon and transponder signals from the TACSAT satellite were measured over a wide geographic area around the magnetic equator. In one series of measurements the beacon amplitude was simultaneously recorded on the ground and airborne. A computer reduction was used to obtain cross-correlation coefficients on the fading data from the two sources. A variable time base was applied to the airborne data to obtain the cross-correlation. Initial results show the airborne time base exhibited a time speedup of 4 to 6 compared with the ground data. That is, the airborne fade rate and frequency was four to six times greater than the ground data fade rate. In a second experiment a psuedo-random coded sequence was sent through the satellite transponder. On the aircraft one demodulator was locked to the downlink sequence while a second demodulator searched the area around the correct code location. In this way the searching code correlates with the direct signal first and with a delayed signal at a later time. A code rate of 300 kbps was used to provide for detection of a 3 microsecond differential delay (900-meter path difference). The results of this test showed that the differential delay during severe fading was less than one microsecond. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1972
- Accession Number
- AD0908842
Entities
People
- Allen L. Johnson
Organizations
- Air Force Research Laboratory