![]() ![]() The latter is especially challenging to measure, as it must be derived from range data, and at a distance of 100 million kilometers, a 1000 kilometer displacement above or below the plane of the spacecraft's trajectory produces only a five meter increase in range. Generally, trajectories lie in the plane of the ecliptic – more specifically, for navigation purposes, in the plane of a triangle defined by the Sun, Earth, and position of the spacecraft – and tracking stations on Earth must be able to assess both the movement of a spacecraft along that plane, as well as any deviation above or below. The Earth, and most planets, all rotate in the same basic plane, like marbles all rolling around on the same plate – this is the so-called plane of the ecliptic. Interplanetary navigation relies on tracking data to determine how fast the spacecraft is moving, and how far away it is from the Earth. It can be observed by anyone who has watched an ambulance go by – the pitch of its siren seems to drop as it speeds away, as the sound wave frequency decreases.) (Doppler shifting occurs for sound waves as well. By measuring the Doppler shift, you can determine spacecraft velocity the bigger the shift, the faster the spacecraft is moving away from Earth. Doppler shift is the stretching out of the wavelength of a radio wave as it travels back to Earth from the receding spacecraft – you send a signal of a known wavelength to the spacecraft, and it sends the same signal back. Velocity is calculated from the Doppler shift of the radio signal. The distance from the Deep Space Network on Earth, to a speeding probe, is calculated by timing how long it takes for a radio signal to travel the round-trip distance between the ground stations and the probe. ![]() These in turn are derived from more basic data: a series of direct measurements of range, and velocity, each made at a particular moment in time. ![]() Just as the invention of a new class of seagoing timepieces – the marine chronometer – revolutionized navigation at sea, so (NASA hopes) will the Deep Space Atomic Clock revolutionize interplanetary navigation.Ī total of six numbers – three for position, and three for velocity – give the location and speed of a spacecraft at any given instant. NASA's hope is that one day soon, both probes and manned vehicles might navigate without the need for time-consuming, complex two-way radio transmissions from the ground-based stations known as the Deep Space Network. This is the Deep Space Atomic Clock, which represents the first generation of a novel class of spaceworthy atomic clocks that could eventually usher in a new era of deep-space exploration. Aside from the spectacular light show (Falcon Heavy is currently the most powerful rocket in the world, with a greater payload capacity than any other rocket except for the Saturn V) the mission also carried a number of important payloads, including the first orbital version of a new, very compact, and highly precise atomic clock. Complex 39A is now used for launches of both Falcon 9, and Falcon Heavy rockets, and the launch of June 30th – the mission known as STP-2, or Space Test Program 2 – was the first time a Falcon Heavy rocket had been launched from the complex at night. ![]()
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