In this answer to Prior to putting spacecraft on a trajectory going a significant fraction of the speed of light, would some things need to be tested on Earth? I wrote:

As far as communications is concerned I can't imagine anything that would have to be tested at such high speed. The regular Doppler effect and relativistic Doppler effect are well understood, and there should be no challenge to building transmitters and receivers for the expected red-shifts from relativistic flight. See answers to Relativistic effects in space mission communications for more.

Just because there "shouldn't be" though doesn't mean that someone won't make a mistake!

The Nature.com article says:

Whose fault was it?

"That's an ESA responsibility," admits (director of science for the European Space Agency (ESA) David) Southwood. Any instructions that need to be sent to the Cassini spacecraft are compiled as a series of software commands by mission scientists, and these are transmitted to the craft from the Jet Propulsion Laboratory in Pasadena, California. All commands relating to the Huygens probe were programmed by ESA.

Southwood says it isn't important who omitted the crucial instruction, because the responsibility runs wider than that: the error should have been picked up during checks. ESA is now mounting an investigation into why the mistake was not spotted. "I'm extremely anxious to learn lessons from this," says Southwood.


  1. Ultimately how did the omission of this command not get caught by anybody at ESA nor anybody at JPL?
  2. Have standards and practices changed now so that missing commands or other problems like this would automatically be caught?
  • 1
    $\begingroup$ perhaps it was broken when they fixed the bigger problm they had -- “We have a technical term for what went wrong here,” British scientist John Zarnecki of the Planetary Science and Space Research Institute of Britain’s Open University told reporters. “It’s called a cock-up.” $\endgroup$ – JCRM Jun 7 '20 at 10:13

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