When did exploration to the inner solar system begin?
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When did exploration to the inner solar system technically begin with the launch of the first lunar flyby satellite?
2 January 1959
No context provided
When did exploration to the inner solar system technically begin with the launch of Pioneer 5 for interplanetary space investigations?
11 March 1960
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When did exploration to the inner solar system technically begin with the launch of Mariner 2, which resulted in the first successful flyby of Venus?
27 August 1962
Timeline of Solar System exploration
https://en.wikipedia.org/wiki/Timeline%20of%20Solar%20System%20exploration
Luna 1 was launched at 16:41 GMT (22:41 local time) on 2 January 1959 from Site 1/5 at the Baikonur Cosmodrome by a Luna 8K72 rocket.[1]
Luna 1
Pioneer 5 (also known as Pioneer P-2, and Able 4, and nicknamed the "Paddle-Wheel Satellite"[3]) was a spin-stabilized space probe in the NASA Pioneer program used to investigate interplanetary space between the orbits of Earth and Venus.
Pioneer 5
The launch of the first lunar flyby satellite was Luna 1 on 2 January 1959. Pioneer 5 was used to investigate interplanetary space between the orbits of Earth and Venus and was launched on 11 March 1960. The first successful flyby of Venus was done by Mariner 2, launched on 27 August 1962.