Bye bye Opportunity joining Spirit

One of my favorite engineering packages was to connect the control center in San Diego to JPL in Los Angeles. Because the mission was only supposed to last 90 days, minimum cost was a primary requirement yet with the reliability of NASA mission circuit.

In a traditional mission circuit, we install two, independent circuits using different physical paths to the control or antenna. Identical routers are at the remote center so if one fails, the other continues. Separate physical paths means a road or construction crew could not cut the line and cut them off. We also provide two UPS units so power loss keeps them running. Mission circuits are by definition at least twice the cost of a regular circuit and often more because of the diverse, independent paths. But the 90 day, Mars rover mission duration meant the circuit was cost constrained.

I designed an asymmetrical network connection:

• DS-3 (45 mbs) - primary circuit that provide voice, command, and data to and from the remote site to a medium sized, 29xx Cisco router.
• T1 (1.2 mbs) - failover circuit that provided voice, command, and bandwidth limited data to and from the remote site to a 17xx Cisco router, the smallest they sold.
• Using Quality of Service - (1) network management, (2) voice, (3) command), and (4) data.
  1. Network management is a low bandwidth access needed to figure out what is going on.
  2. Voice has hard voice, timing requirements but is relatively low bandwidth
  3. Command is relatively low bandwidth but necessary to communicate with the rovers. But the distance between Earth and Mars means the rovers have substantial, on-planet operation.
  4. Data is shared between data quality, e-mail, and eBay bids.
  5. The 4-wire voice over IP sends the transmit signal over one pair of lines and a shared receive signal on another pair of lines into the legacy, 4-wire, NASA mission voice network. The interface was located in the 3d building at JPL from the internet data building.

We ran this network for several years until Cisco declared these routers "end-of-life" and everything was replaced at 3-4x times the cost. But more importantly, the rovers had lasted years, orders of magnitude longer than expected. They actually wore out some of their scientific instruments, the rock borers.

So I mourn their loss not just because of the science they provided (and might provide) but because I had a chance to contribute to their success. We saved my salary x2 because I tweaked the minimum needed to build a mission qualified circuit ... and now I'm retired.

Bob Wilson