A satellite is an object that falls from the sky and kills a Sim in The Sims 2. They can be described as a smoking, trashy mass of debris, but one can tell what they are exactly with the buy mode description or a photo looking at the particular Sim's death.
When Sims look at clouds or stargaze on the ground, there's a 1% chance they might be crushed by a satellite. If the check is true, the satellite will fall after 5 to 24 animation cycles, where in every 3 cycles, a thought balloon will appear on a Sim's head. If Sims quit the interaction before the satellite falls, the death will not occur.
The game only checks whether the death will occur or not at the beginning of the interaction. Due to this, looking at clouds or stargazing longer than 24 animation cycles will not increase the chance of dying. Sims will have to repeat the process from the beginning until the 1% chance condition is met.
When a satellite falls, it's worth §1,999, but the price depreciates rapidly, so it is best to sell the satellite immediately for the best price. Being crushed by a satellite is one of the two ways a Servo can be killed.
In The Sims 3, Sims can spot Satellites, among other astronomical features, while using a telescope to raise the Logic skill. Sims report their discovery remotely, name it, and thus earn a few Simoleons. Other Sims can spot pre-discovered satellites while stargazing. Satellites cannot kill Sims in The Sims 3.