Very Remote Debugging

By Susam Pal on 03 Sep 2007

There is a wonderful story about a legendary Lisp debugging story in the second chapter of the book Practical Common Lisp by Peter Seibel. Quoting the story here:

An even more impressive instance of remote debugging occurred on NASA's 1998 Deep Space 1 mission. A half year after the space craft launched, a bit of Lisp code was going to control the spacecraft for two days while conducting a sequence of experiments. Unfortunately, a subtle race condition in the code had escaped detection during ground testing and was already in space. When the bug manifested in the wild--100 million miles away from Earth--the team was able to diagnose and fix the running code, allowing the experiments to complete. One of the programmers described it as follows:

Debugging a program running on a $100M piece of hardware that is 100 million miles away is an interesting experience. Having a read-eval-print loop running on the spacecraft proved invaluable in finding and fixing the problem.

The original source of this story is an article called Lisping at JPL written by Ron Garret in 2002. This story occurs in the section called 1994-1999 - Remote Agent of the article.