<P> A variation on terrestrial celestial navigation was used to help orient the Apollo spacecraft en route to and from the Moon . To this day, space missions such as the Mars Exploration Rover use star trackers to determine the attitude of the spacecraft . </P> <P> As early as the mid-1960s, advanced electronic and computer systems had evolved enabling navigators to obtain automated celestial sight fixes . These systems were used aboard both ships and US Air Force aircraft, and were highly accurate, able to lock onto up to 11 stars (even in daytime) and resolve the craft's position to less than 300 feet (91 m). The SR - 71 high - speed reconnaissance aircraft was one example of an aircraft that used a combination of automated celestial and inertial navigation . These rare systems were expensive, however, and the few that remain in use today are regarded as backups to more reliable satellite positioning systems . </P> <P> Intercontinental ballistic missiles use celestial navigation to check and correct their course (initially set using internal gyroscopes) while flying outside the Earth's atmosphere . The immunity to jamming signals is the main driver behind this seemingly archaic technique . </P> <P> X-ray pulsar - based navigation and timing (XNAV) is an experimental navigation technique whereby the periodic X-ray signals emitted from pulsars are used to determine the location of a vehicle, such as a spacecraft in deep space . A vehicle using XNAV would compare received X-ray signals with a database of known pulsar frequencies and locations . Similar to GPS, this comparison would allow the vehicle to triangulate its position accurately (± 5 km). The advantage of using X-ray signals over radio waves is that X-ray telescopes can be made smaller and lighter . On 9 November 2016 the Chinese Academy of Sciences launched an experimental pulsar navigation satellite called XPNAV 1 . SEXTANT (Station Explorer for X-ray Timing and Navigation Technology) is a NASA - funded project developed at the Goddard Space Flight Center that is testing XNAV on - orbit on board the International Space Station in connection with the NICER project, launched on 3 June 2017 on the SpaceX CRS - 11 ISS resupply mission . </P>

In order to navigate the mars rover which electronic navigation system must be used