Sputnik 1, the first man-made satellite to orbit the Earth, only weighed 184 pounds and was just a 23-inch diameter sphere made of a "AMG6T" aluminium-magnesium-titanium alloy, with four protruding antennas, so it did not have much room for instrumentation. It had a one-watt radio transmitter that sent out radio pulses at two different frequencies (20.005 and 40.002 MHz).

In addition to the radio transmitter, there was an internal fan unit and temperature/barometric sensor to monitor the interior of the sphere, which was sealed and pressurized with nitrogen gas. The radio was used in nominal conditions to transmit a steady pulse every 0.3 seconds to signal to the world that the satellite was indeed on orbit, but if the barometric and temperature sensors recorded a spike or sudden change, then the duration of the otherwise steady 0.3 second radio pulse was designed to change to notify the ground monitors. That never happened though.

The behavior of Sputnik's radio signals as they were being received on Earth were able to provide data on the effects of radio wave propagation through our planet's ionosphere at different altitudes. The satellite was placed onto an initial elliptical orbit with a perigee of 223 kilometers and an apogee of 950 kilometers, and the degradation in that orbit over time was also studied to determine the effects of atmospheric drag on the satellite. The radio lasted for 21 days before the silver-zinc onboard batteries ran out and it finally went silent. Sputnik 1 finally re-entered and burned up in Earth's atmosphere on January 4, 1958.

While its primary purpose was most definitely more propaganda relevant than scientific, Sputnik 1 was able to provide a bit of science data using the methods I described above.