Last best shot of Pluto before scheduled radio scilence
courtesy NASA, SOURCE
Pluto: Robot Explorer expected to Call Home Tonight/Updated

Posted: Jul 14, 2015 08:37 pm EDT

(Tina Sjogren/story updated July 14, 23.00 EDT) Coming out of ‘data-gathering mode’ New Horizons is expected to call home tonight and report mission accomplished on Pluto.


Story update: Signals from the spacecraft arrived as planned at 8:52:37 p.m. Eastern time July 14. Data has been collected and the spaceprobe is outbound from Pluto. First images from the close encounter are expected on Wednesday.


The size of a big fridge carrying a 2-meter dish antenna; the probe is fitted with a cold-resistant digital camera with telephoto lens (20 cm aperture) and a miniature spectrometer-combo instrument.


The craft shoots pictures of some planetary features down to 50 meters resolution at closest approach and detects chemicals by the amount of sunlight they absorb. A foil collector measures how fast electrons bounce off of it.  




Commonly on space-probes, onboard antennas and small printed signal-processing circuit boards beam em-signals back to earth using object’s atmospheres as fingerprint filter. Because of the unique speed and distance of New Horizons; earth beams to the probe instead (on the Xband) since only a large, ground-based antenna can provide a strong enough signal. 


Ears on earth is the Deep Space Network - three dishes spaced out over three continents for continuous connection. 




There are 2 computer systems (Command&Data handling, Guidance&Control processor) in 4 computers.  Mongoose-V processor, a 12 MHz radiation-hardened version of the MIPS R3000 CPU.


Data storage on two low-power solid-state recorders (one primary, one backup) holding up to 8 gigabytes each. Multiple clocks and timing routines are implemented in hardware and software to help prevent faults and downtime.


Speed and Power 


New Horizons was designed specifically for the cold and dark conditions of the Kuiper belt. The craft got most of its speed (roughly 23 km/s, less during flyby) in the initial launch and a 4 km/s sling-shot like gravity boost by Jupiter that saved it 3 years of travel. 


16 thrusts placed around the craft are used mainly for navigational adjustments. Space probes navigate by star tracking cams and software, gyroscopes, accelerometers and digital solar sensors.


Overall power needs (228 watts) are supplied by solar panels and plutonium(11 kg, non-weapons grade) generators. There are no batteries; the power is distributed by capacitor and circuit breakers.



Alpine style packaging


Because of the great distance of Pluto and the Kuiper belt; New Horizons payload is sort of like the rigid packing involved in an unsupported North Pole expedition or alpine style Himalaya ascents. 


All electronics, 9 boards, are housed together. Collectively the instruments at New Horizons draw less than 28 watts and - in planetary exploration - the payload is the most miniaturized yet (think Arduino/Raspberry Pi scale).


The weight/power constraints also forced all instruments to be fixed rigid to the probe. The whole spaceship must be turned away from Pluto for the antennas to point back to earth which explains the dedicated ‘data-collection’ mode today.


Closest Pluto approach is about 7,750 miles above the surface -- roughly the same distance from New York to Mumbai. In the final phase of its mission, New Horizons will head deeper into the Kuiper Belt in search of icy comets and objects that may be the original source of water in our solar system.


The largest structure in our planetary system, the Kuiper Belt is believed to be the source of short-term comets (those with orbits of 200 years or less), and may be home to more than 100,000 miniature worlds larger than 100 kilometers. More about the mission here.



Pluto shows Mystery Face for One Last Time

Final Countdown to Last Outpost in our Solar System 


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