| Autor: |
Sami W. Asmar, Timothy P. Krisher, David D. Morabito |
| Rok vydání: |
2002 |
| Předmět: |
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| Zdroj: |
1993 IEEE International Frequency Control Symposium. |
| DOI: |
10.1109/freq.1993.367479 |
| Popis: |
Radiometric tracking Doppler measurements of the signal transmitted by the Galileo spacecraft using an ultrastable oscillator (USO) as a frequency reference have been acquired by antennas of the NASA Deep Space Network between Dec. 1989 and Nov. 1991. The USO is a dual oven-controlled oscillator with an AT-cut quartz crystal (SiO/sub 1/) resonator. The output frequency of 19.124980 MHz is multiplied by 120 to produce the transmitted signal frequency (/spl sim/2.29 GHz). The average Allan deviations at 1-s and 10-s correlate well with spacecraft range, and fall as /spl tau//sup -1/. This is consistent with white PM noise dominating at these times scales due to the low SNR's expected from using the low gain antennas. The Allan deviations at 100-s and 1000-s agree with pre-flight USO stability results at these time scales. The Galileo USO appears to be healthy and functioning normally. > |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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