The Galileo satellites transmit different message types: F/NAV type correspond to the Open Service (OS), I/NAV message correspond to the Safety of Life (SoL) and C/NAV to Comercial Service (CS).
The navigation message data are transmitted on each data component as a sequence of frames. A frame is composed of several sub-frames, and a sub-frame in turn is composed of several pages. Being this last one the basic structure for building the navigation message. Read more…
It is the most inexpensive, compact, and widely used type of atomic clock, used not only in Galileo and GPS but also to control the frequency of television stations, cell phone base stations, etc.
Voyager 1 has marked one of the most significant technological achievements in the annals of the history of science. It is currently where no probe has gone before.
It is a 722 kg spacecraft launched by NASA on 5 Sept 1977 to study the outer Solar System. Currently it is the farthest manmade object from Earth. Read more…
An atomic clock works like a conventional clock but the time-base of the clock, instead of being an oscillating mass as in a pendulum clock, is based on the properties of atoms when transitioning between different energy states.
When an atom is excited by an external energy source, it goes to a higher energy state. Then, from this state, it goes to a lower energy state. In this transition, the atom releases energy at a very precise frequency which is characteristic of the type of atom. Read more…
Video explanation on how PHM works:
The Passive Hydrogen Maser (PHM) is the master clock on the Galileo satellite’s payload. Its extremely good performance makes it the most stable of all clocks currently in space, better than 1 nanosecond per day. Some other features: 18 Kg of mass, 28 liters of volume and 20 years lifetime.
The hydrogen maser uses the properties of the hydrogen atom to serve as a precision frequency reference. But, how does it work? Let’s see what is the process: Read more…
GIOVE-B (Galileo In-Orbit Validation Element) was launched by a Soyuz rocket from Baiknour on 27 April 2008, carrying the most accurate atomic clock ever flown into space at that moment.
The 500 kg satellite was left into a circular orbit at an altitude of 23,173 km, inclined at 56 degrees to the Equator, 3 hours and 45 minutes after the launch. It makes a complete journey around the Earth in 14 hours and 3 minutes. Read more…