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Where Are The
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The two Voyager spacecraft continue to operate, with some loss in subsystem redundancy, but still capable of returning science data from a full complement of VIM science instruments. Both spacecraft also have adequate electrical power and attitude control propellant to continue operating until around 2025 when the available electrical power will no longer support science instrument operation. At this time science data return and spacecraft operations will end.

Spacecraft electrical power is supplied by Radioisotope Thermoelectric Generators (RTGs) that provided approximately 470 w of 30 volt DC power at launch. Due to the natural radioactive decay of the Plutonium fuel source, the electrical energy provided by the RTGs is continually declining. At the beginning of 2008, the power generated by Voyager 1 had dropped to ~ 285 w and to~ 287 w for Voyager 2. Both of these power levels represent better performance than the pre-launch predictions, which included a conservative degradation model for the bi-metallic thermocouples used to convert thermal energy into electrical energy. As the electrical power becomes less and less, power loads on the spacecraft must be turned off in order to avoid having demand exceed supply. As loads are turned off spacecraft capabilities are eliminated. The following table identifies the year when specific capabilities have or will end as a result of the available electrical power limitations.

 
VOYAGER 1
VOYAGER 2

Power Off Plasma (PLS) Subsystem.

2007-032

PLS Heater

2007-130

Power Off Planetary Radio Astronomy Experiment (PRA)

2008-015

2008-052
Terminate scan platform and Ultra Violet (UV) observations
~EOY 2010
1998-316
Termination of Data Tape Recorder (DTR) operations
~2015*
2007-248**
Termination of gyro operations
~2016
~2015
Initiate instrument power shutdown
~2020***
~2020***
Can no longer power any single instrument
No earlier than 2025
No earlier than 2025

* Limited by ability to capture 1.4 kbps data using a 70m/34m antenna array
In order to maximize the duration of the fields and particles data acquisition capability,

** Voyager 2 DTR operations was no longer needed due to a failure on the high waveform receiver on the Plasma Wave Subsystem (PWS) on June 30th, 2002.

Termination of gyro operations ends the capability to calibrate the magnetometer instrument with magnetometer roll maneuvers (MAGROLs). These maneuvers are performed 6 times a year, on each spacecraft, and consist of a spacecraft attitude maneuver of 10 successive 360 degree turns about the roll axis. Data from a MAGROL allow the spacecraft magnetic field to be determined and subtracted from the magnetometer science data. This is important since the spacecraft magnetic field is larger than the solar magnetic field being measured. The termination of gyro operations also means an end to the attitude maneuvers used to check the combined calibration of the Sun Sensor and the High Gain Antenna pointing direction for maintaining communications with the ground.

*** Science Instruments power shutdown order has not been determined.

The following experiments are expected to be operating by 2020:

Voyager 1: Low-Energy Charged Particles, Cosmic Ray Subsystem, Magnetometer and Plasma Wave Subsystem.

Voyager 2: Low-Energy Charged Particles, Cosmic Ray Subsystem, Magnetometer, Plasma Wave Subsystem and Plasma Subsystem.

 
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