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RF Shorts for July 18, 2014

ISEE-3 Satellite Reactivation Update

I've previously reports on the ISEE-3 "reboot" effort. The volunteers working on the project were able to establish communication with the spacecraft, but have run into some problems in getting the thrusters to work.

The latest July 16 Status Report offered some hope that they might be able to get the thrusters working and change the spacecraft's orbit. Here’s a description of the ongoing efforts:

"During our interaction with ISEE-3 today, we tried a variety of valve and thruster selections using both sides of the propulsion system combined with tank and fuel line heating. Although we met with limited success we did get several instances of thrust (the main intent) and also a change in the Fine Sun Sensor angle of the spacecraft. So, something changed the trajectory of ISEE-3 albeit slightly. Also, the temperatures in the fuel tanks only rose a little bit which is what you'd expect of they were still full of fuel. This is good news since we were concerned for a while that there might have been a loss of fuel and/or pressurant."

The narrative continues: "…we're analyzing the data and trying to sleuth out how we got the momentary thrust and then apply that to our next interaction with the spacecraft. We have applied for an extension to our license from NASA to transmit to the spacecraft and are awaiting their reply."

A previous status report stated: "Our troubleshooting today eliminated some suspected causes of propulsion system problems. We do not think any of the valves are malfunctioning. Right now we think there is a chance that the nitrogen used as a pressurant for the mono-propellant hydrazine propulsion system may have been depleted. That said, we still have a number of troubleshooting options yet to be explored. We have a DSN pass scheduled for Friday that will allow us to recalibrate our location information and trajectory plans for ISEE-3. Even if the L-1 halo orbit is no longer an option, we do have plans to use ISEE-3 for science in other locations within the inner solar system after the lunar flyby on 10 August."

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Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.