The series was filmed in California, USA during season one, and British Columbia, Canada during seasons two and three.
In May 2001, the series was cancelled.
By reverse-engineering the alien technology, they were able to create a time machine. The time machine is not the Chronosphere itself, but encompasses the Chronosphere's hangar and the supporting equipment. The Chronosphere is mainly just a vessel to transport the Chrononaut through space and time.
The time machine uses Element-115 salvaged from the Roswell crash. This transuranic element allowed them to generate a time distortion field around the Chronosphere which will displace it through space and time. The sphere is usually teleported away from the hangar and into space, after which the chrononaut, Frank Parker, will steer the sphere towards the required space and time coordinates (referred to as 'flying the needles' in the early episodes).
While it may appear that the time machine is the Chronosphere itself, this is not the case. The Chronosphere has its own power source for navigation and avionics, but it doesn't produce the time displacement field for time travel (explained in Season 1, Episode 9 - "As Time Goes By").
Instead, the Element-115 fuel source, the reactor and the gravitational field generators are located outside the Chronosphere. A waveguide conduit connects the reactor to the Chronosphere, whereby the gravity wave generated by the Element-115 fuel source is "pumped" towards the sphere. The sphere will then latch on to this gravity wave whereby it is converted into a time displacement field, which is a localized region of spacetime distortion (see Season 1, Episode 9 - "As Time Goes By"). Due to the limited amount of Element-115 fuel, it has to be used sparingly. Furthermore, due to the limitations of the reactor size and output power, the time displacement field has sufficient energy to send the Chronosphere back in time for only seven days (see Season 1, Episodes 1 and 2).
It was also mentioned that they can only go back in time seven days due to the quantity of the fuel source. The Element-115 fuel source can "regenerate". It will be depleted after each backstep and it will take seven days for the fuel to regenerate to an amount necessary to charge the reactor up to 100 percent (see Season 3, Episode 8 - "Tracker").
However, in another episode - Season 3, Episode 21, "Born in the USSR" - the Soviets mentioned that they encountered a mathematical limitation of the time travel mechanism that they were working on, in which it would appear that time travel is limited to only seven days to the past, and nothing more than that. They mentioned that they were unable to overcome this "barrier".
Project Backstep was indicated to still exist many decades into the future. In Season 2, Episode 23 - "The Cure", an NSA agent from the future traveled far back in time to stop a doctor from developing a cancer cure. He revealed that this cure would mutate and cause an epidemic that brought mankind to the edge of extinction. The NSA of the future salvaged more Element-115 from another saucer crash, and used all the Element-115 fuel that they had at one go, thus enabling the Chronosphere to be transported decades into the past.
These aliens are referred to as "Greys" and were said to originate from the Zeta Reticuli system. Donovan explained to Parker in the pilot episode that in order to cross the vast distances between stars, the aliens have developed a propulsion technology that bent space and time (similar to a warp drive).
The NSA have been reverse-engineering the technology left behind from the crash, but was still unsuccessful at replicating a warp drive for faster-than-light travel. They have, however, harnessed the alien fuel source, Element-115, to bend spacetime and the end result was the ability to time travel (explained by Donovan in Season 1, Episode 1).
It would appear that the aliens, who were used to faster-than-light travel, had developed cognitive functions that made them aware of multiple timelines and realities. This was revealed in the first season finale in which the alien Adam was aware of the timelines before and after Parker's backstep (Season 1, Episode 21 - "Lifeboat").
The aliens also had advanced surgical procedures whereby an implant was able to bridge the signals in a damaged spinal cord, allowing paralyzed aliens to walk again (Season 2, Episode 6 - "Walk Away"). Ballard tried out this implant and it enabled him to walk again, but the neural profile of Adam (from which the implant was taken) was also imprinted in the implant, and it gradually 'leaked' into Ballard's consciousness, effectively causing the residual 'mind' of Adam to possess Ballard.
Other than the Zeta Reticulians, another extraterrestrial entity that was shown on the series was the "Time Gremlin" (Season 2, Episode 11 - "Time Gremlin").
The Chronosphere passed through a wormhole rift just outside of Earth orbit and was drawn towards it due to its gravitational effects. While lingering around the wormhole's event horizon, an alien creature caught on to the Chronosphere and followed it back to Earth. In transit, the gremlin damaged the sphere, causing Frank Parker to "lose the needles" for the very first time, leading to his first failed Backstep.
It was later revealed that the creature originated from the Hydra system. Ballard somehow traced the origin of the wormhole and suggested to the Backstep team that they should launch the sphere into space again with the hatch open, and let the gremlin return to where it came from.
The Soviet time travel project also had possession of Element-115 from a similar alien craft crash in Siberia (Season 3, Episode 21 - "Born in the USSR"). However, Soviet physicists were unable to refine the physics needed to harness the ability of Element-115 for spacetime distortion.
In the episode "As Time Goes By", a Russian time machine from the future returned to the past to visit Project Backstep. The Russian chrononaut tried to steal the Element-115 fuel source and damage the Chronosphere. The Russian time machine was shown to be powered by a "Photon Reactor" that has a similar output to a hydrogen bomb (according to Ballard), something that Ballard is also working on. This allowed the time machine to generate sufficient power to create its own localized time displacement field without relying on Element-115. The Russian chrononaut also claimed that his time machine is able to travel forward in time, not just backward.