Another question asks why Spirit and Opportunity weren't launched together. My gut response was that multiple-payload launches were less common then than they are today, but I don't actually know if that's true.

What was the first single launch to put two or more independent payloads into Earth orbit?

What was the first time, if ever, that a single launcher put two independent spacecraft on trajectories leaving Earth's sphere of influence?

Not included: multiple-warhead military applications, or balloons deployed from Mercury spacecraft or Gemini's "rendezvous evaluation pod"; the payloads have to go into different orbits, or at least phased substantially in the same orbit.

• Related, but not the same (doesn't deal with the historical part). 1978 - Pioneer is pretty old though :). Does it have to separate in Earth orbit? Or be a set of duplicate probes which are redundant to each other? – Magic Octopus Urn May 20 '19 at 21:41
• Oh wow, I didn't know about that one! I'll at least throw an upvote at it if you make it an answer. I didn't specify where or how they separated, and they were on different trajectories for weeks between separation and Venus arrival. – Russell Borogove May 20 '19 at 23:36
• I suggest splitting this question in two – Joe Jobs Jan 22 at 23:02

I can't be sure this is the first attempt, but it might be the strangest-looking: GRAB + ELINT. However it was unsuccessful, and in a very big way.

The item on top is called GRAB 1 for Galactic Radiation and Background. However that's a cover:

Galactic Radiation and Background (GRAB) was the covername for Project Dyno ELINT intelligence satellites operated by the U.S. Naval Research Laboratory (NRL) shortly after the Cold War U-2 incident of 1960. The satellites carried two sets of instruments: an unclassified experiment (called Solrad) and a then-classified payload to collect electronic intelligence (ELINT) (called Tattletale). Of five attempted launches, two missions were successful. The program is also known by the later codeword Canes.

Incidents

During the second launch attempt, the Thor booster shut down 12 seconds early, and the flight was subsequently terminated by Range safety. As fragments fell on Cuba, subsequent launches from Cape Canaveral flew a dogleg trajectory to reach 70 degree inclination.

I'm not yet sure if this is the origin of doglegging to orbit, so I've asked Which launch was the first to use a dogleg maneuver?

• That thing looks mighty goofy (in a cool way)-- I have to wonder if the spiral was performing something, may ask after I look around a bit and link here. – Magic Octopus Urn May 21 '19 at 23:37
• @MagicOctopusUrn search "spiral" and my user name. You could consider adding the antenna tag to your search by including [antenna] in your search string, unless of course someone has thoughtfully deleted the tag from my question(!) as well ;-) – uhoh May 21 '19 at 23:44

Thor Ablestar launched on 22 June 1960

• SOLRAD 1, a GRAB satellite
• Transit 2A, an early naval navigation satellite

Apollo 9, launched on March 3, 1969 had a Lunar Module and a Command Module

If the Moon is considered into the Earth's sphere of influence then:

Viking 1 mission to Mars, launched August 20, 1975 - had an orbiter and a lander.

if orbiter-lander are not good then:

Mars Cube One (or MarCO) was a Mars flyby mission launched on 5 May 2018 alongside NASA's InSight Mars lander mission. It consisted of two nanospacecraft, MarCO-A and MarCO-B

• Answers should cite their supporting sources, otherwise there's no way for future readers to distinguish good, accurate answers from those with random fake information. Many know that you really work hard at this, but an answer needs to stand on its own, not the reputation of the author. Thanks! – uhoh Jan 23 at 1:02