In 1973 we had no large orbiting space station circling the Earth at a time when one of the largest UFO flaps to hit the planet was in progress. A document that was found indicates that the location was over the southwestern Indian Ocean during revolution # 1863. Astronauts Alan Bean, Owen Garriott and Jack Lousma spotted what they described as a red "satellite", which they photographed and mentioned during a subsequent debriefing. We have radio conversation (transcript only) with Houston CapCom about 4.5 hours after the sighting of this object. There was no man-made satellite that could explain this sighting and hence the object was truly anomalous.
Tasked with everything from maintenance to experiments both scientific and medical, the crew of Skylab III faced a number of crises during their short tenure (July 28, 1973, to September 25, 1973,) all of which were thankfully resolved and one occurrence of a possible otherworldly nature which never was explained, an unidentified object that followed the space lab purportedly undetected by NASA or NORAD.
A few days before returning to Earth and while out of radio contact, Garriott took photos of an anomalous object from Skylab's wardroom window. The first recorded mention of the incident was between the astronauts and CAPCOM some four and a half hours later:
LOUSMA: "Did you tell him about that satellite we saw?
BEAN: Yes, we saw a great satellite. We didn't know if we told you about it.
LOUSMA: The closest and brightest one we've seen.
BEAN: Huge one.
LOUSMA: We've seen several. It was a red one.
CAPCOM: No, you may have told somebody, but it wasn't this team. I don't remember hearing about it.
LOUSMA: I guess we didn't report it. It was reflecting in red light and oscillating at, oh, counting it's period of brightest to dimmest, about ten seconds. It led us into sunset. That was about three revs ago, I think. Something like that, wasn't it Owen?
(NOTE: Astronaut Owen does NOT respond to this question, and the topic of conversation abruptly changes. There is no information available regarding whether or not this sighting was brought to the attention of Mission Control prior to this radio contact 4.5 hours after the event).