Speed of the Voyager Space Probes

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Bibliographic Entry	Result (w/surrounding text)	Standardized Result
McGraw-Hill Encyclopedia of Science and Technology. vol. 17. New York: McGraw-Hill, 1992. 138-141.	"Voyager 1 is now leaving the solar system, rising above the ecliptic plane at an angle of about 35° at a rate of about 3.2 × 10⁸ mi (5.2 × 10⁸ km) a year …. Voyager 2 is also leaving the solar system, diving below the ecliptic plane at an angle of about 48° at a rate of about 2.9 × 10⁸ mi (4.7 × 10⁸ km) a year."	16.49 km/s (Voyager 1) 14.90 km/s (Voyager 2)
Voyager Mission Status. Jet Propulsion Laboratory. 1995. [This page no longer exists at this URL.]	"The Voyager 1 spacecraft is departing the solar system at a speed of 17.46 km/s …. The Voyager 2 spacecraft is departing the solar system at a speed of 16.08 km/s."	17.46 km/s (Voyager 1) 16.08 km/s (Voyager 2)
Voyager Mission Operations Status Report: Range, Velocity and Round Trip Light Time. Voyager Project. Jet Propulsion Laboratory (JPL). Pasadena, CA.	"Velocity Relative to Sun (km/sec) as of 6/13/97: Voyager 1 17.374 Voyager 2 15.957"	17.374 km/s (Voyager 1) 15.957 km/s (Voyager 2)

Voyager 1 was launched in September 1977, a month after when Voyager 2 which was launched in August 1977. Voyagers 1 and 2 are different from other space probes in that they were designed to go further than all other space craft and leave the solar system. My goal was to find their speeds as they leave the solar system.

After doing some research on the subject, I found that the information from the two different sources which I had, gave me conflicting measurements. In Mc Graw Hill's Encyclopedia of Science and Technology it said that the speed of Voyager 1 as it leaves the solar system is 16.49 km/s. But in the article, "Voyager Mission Status,"by NASA it says that Voyager 1 is leaving the solar system at a speed of 17.46 km/s. The same differences appeared when I compared both sources for the speed of Voyager 2. McGraw-Hill says 14.90 km/s, and NASA says 16.08 km/s.

If it were up to I would have to go with the numbers that NASA gave. Due to the fact that the original numbers that Mc Graw's Encyclopedia gave me were 5.2 × 10⁸ km/yr for Voyager 1 and 4.7 × 10⁸ km/yr for Voyager 2. When I saw these units I had to convert them to km/s. But the resultant conversions are too close to the numbers that was supplied by NASA. Another reason why they could differ is probably because both NASA and McGraw-Hill used different methods to find the speeds of the Voyager space probes as they leave the solar system.

Patrice Pean -- 1997

Bibliographic Entry	Result (w/surrounding text)	Standardized Result
NASA/JPL. Advances in the Astronautical Sciences. AAS Publications, 1981 cited in Hall, Stephen S. Mapping the Next Millenium. New York: Random House, 1992. 50.	"Voyager 1 3.50 AU/yr Voyager 2 2.92 AU/yr, 2.90 AU/yr, 3.04 AU/yr, 3.24 AU/yr, 3.39 AU/yr [highlighted], 3.76 AU/yr, 4.09 AU/yr, 3.96 AU/yr Pioneer 10: 2.39 AU/yr Pioneer 11: 2.22 AU/yr"	16.6 km/s (Voyager 1) 13.8–19.4 km/s (Voyager 2)

Editor's Supplement -- 2000

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