consisted of three silver-zinc batteries, developed at the All-Union Research Institute of Power Sources (VNIIT) under the leadership of Nikolai S. Lidorenko. Two of these batteries powered the radio transmitter and one powered the temperature regulation system. The batteries had an expected lifetime of two weeks, and operated for 22 days. The power supply was turned on automatically at the moment of the satellite's separation from the second stage of the rocket. The satellite had a one-watt, radio transmitting unit inside, developed by Vyacheslav I. Lappo from NII-885, the Moscow Electronics Research Institute, that worked on two frequencies, 20.005 and 40.002 MHz. Signals on the first frequency were transmitted in 0.3 s pulses (near f = 3 Hz) (under normal temperature and pressure conditions on board), with pauses of the same duration filled by pulses on the second frequency. Analysis of the radio signals was used to gather information about the electron density of the ionosphere. Temperature and pressure were encoded in the duration of radio beeps. A temperature regulation system contained a fan, a dual thermal switch, and a control thermal switch. If the temperature inside the satellite exceeded , the fan was turned on; when it fell below , the fan was turned off by the dual thermal switch. If the temperature exceeded or fell below , another control thermal switch was activated, changing the duration of the radio signal pulses. Sputnik 1 was filled with dry nitrogen, pressurized to . The satellite had a barometric switch, activated if the pressure inside the satellite fell below 130 kPa, which would have indicated failure of the pressure vessel or puncture by a meteor, and would have changed the duration of radio signal impulse. While attached to the rocket, Sputnik 1 was protected by a cone-shaped payload fairing, with a height of . The fairing separated from both Sputnik and the spent R-7 second stage at the same time as the satellite was ejected. Tests of the satellite were conducted at OKB-1 under the leadership of Oleg G. Ivanovsky. Launch and mission The control system of the Sputnik rocket was adjusted to an intended orbit of , with an orbital period of 101.5 minutes. The trajectory had been calculated earlier by Georgi Grechko, using the USSR Academy of Sciences' mainframe computer. The Sputnik rocket was launched on 4 October 1957 at 19:28:34 UTC (5 October at the launch site) from