SSP – Surface Science Package
SSR – Solid-State Recorder
TandEM – Titan and Enceladus Mission
TiME – TItan Mare Explorer
TNO – Trans-Neptunian Object
TSSM – Titan Saturn System Mission
UTC –Universal Time Coordinated
Valkyrie – Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer
VASIMR – VAriable Specific Impulse Magnetoplasma Rocket
VR – Virtual Reality
WHC – Waste Hygiene Compartment
Metric to English Conversions
Author’s note: It is assumed that by the time the events of this novel take place, the United States will have joined the rest of the world and will be using the International System of Units, the modern form of the metric system.
Length:
centimeter = 0.39 inches
meter = 1.09 yards, or 3.28 feet
kilometer = 1093.61 yards, or 0.62 miles
Area:
square centimeter = 0.16 square inches
square meter = 1.20 square yards
square kilometer = 0.39 square miles
Weight:
gram = 0.04 ounces
kilogram = 35.27 ounces, or 2.20 pounds
Volume:
liter = 1.06 quarts, or 0.26 gallons
cubic meter = 35.31 cubic feet, or 1.31 cubic yards
Temperature:
To convert Celsius to Fahrenheit, multiply by 1.8 and then add 32
Excerpt: The Titan Probe
January 14, 2005, Titan
Huygens awoke at 04:41 a.m. All three preprogrammed timers punctually activated the probe named after the Dutch astronomer Christiaan Huygens. Its main computer ran the test program. The sensors were in working order. Now the scientific instruments were triggered, step by step. First diagnosis—it was in free fall. Everything was going according to plan.
Twenty days ago, a spring mechanism had separated it from the Cassini probe, its ride that had brought it to the ringed planet Saturn over the course of seven years—almost two billion kilometers, though Huygens had noticed little about this long journey. Data packages had been sent from Earth on 16 occasions to run health checks.
Huygens was racing toward Titan at 17 times the speed of sound. No piece of technology made by humans had yet landed on this moon, which resembled the moon of Earth like no other object in the solar system, yet was also so very different from it. The control software of Huygens was prepared for all kinds of surprises, because its programmers did not know much about Titan when the probe was launched.
The countdown continued. The probe was still in freefall toward its destination, which was located somewhere south of the equator. Four hours had gone by when the sensors reported the first particles of the atmosphere hitting its heat shield. The air rapidly became denser. Friction heated the cone-shaped heat shield at its bottom, and at the same time it decelerated the probe, within four minutes, to just above the speed of sound on earth. The pressure sensors transmitted a signal to the main computer. A charge was triggered, and the controlled explosion released the main parachute. At first, Huygens fell blindly, but 30 seconds later the probe moved slowly enough to blast off the no-longer-needed heat shield. Now the instruments started their work, until a warning message reached the computer—one of the radio modules had failed because a person on Earth had forgotten to send the activation command. There was no time for calling back. On Earth, it would be several hours before anyone noticed what had happened. The automatic system decided to continue its mission.
The probe was 150 kilometers above the surface. The moon now covered most of its field of view. A light brown haze impeded its vision. A fierce east wind, many times stronger than winds of hurricane strength on Earth, hit the parachute and pulled it along. At an altitude of 100 kilometers, Huygens separated its main parachute and deployed the smaller stabilizing chute, as the atmosphere was now so dense the smaller one would adequately decelerate the probe. As Huygens descended, the wind gradually faded away. The haze still impeded the view downward, but the scene became clearer with each passing second. The probe was aiming for a dark brown valley located inside a lighter-colored hilly area. In its direction of travel, the instruments discovered two dark, parallel lines, like dunes on Earth, though probably many times bigger.
There was another layer of haze below Huygens. It was lit by the light of the sun, and almost looked like a fancy bed sheet covering the short mountains of Titan. The disk of the sun appeared reddish, and small—about the size of a car headlight at a distance of 150 meters. The Huygens Atmospheric Structure Instrument (HASI) analyzed the air and discovered a lot of nitrogen, some methane, and a little bit of hydrogen.
The cameras of the Descent Imager / Spectral Radiometer (DISR) saw the mountains grow below the probe as it approached its destination valley. They appeared cragged, like high mountains on Earth. Measurements showed, however, that they only rose a few hundred meters above their surroundings. There was no snow, but the mountains were made of ice. Creeks had carved themselves into their slopes, just like the meltwater rivers of the European Alps.
At an altitude of eight kilometers, the direction of the wind changed. Now it drove the chute westward. Huygens could not intervene. At 11:38 hours, the probe landed on the surface of Titan with a speed of 18 kilometers per hour. Even though it weighed almost 300 kilograms, it bounced off the surface several times due to the moon’s low gravity. Its cameras looked around. Huygens had landed in an apparently dry area that resembled a rocky desert on Earth. Around it were several fragments that looked like boulders, randomly placed as if scattered by a bored giant. Otherwise, the ground appeared to be covered by sand. Yet Huygens was not on Earth. It was cold here, very cold—minus 180 degrees. During its descent, the probe had been heated by friction, so now wisps of fog, evaporated methane, rose from the ground. The boulders were not made of granite or sandstone but of ice, just like the grains of sand on which Huygens had landed. The gas chromatograph proved the ice was impure and contained many organic compounds.
Huygens had a mission. If a probe was capable of being happy, it would be happy now. Its instruments recorded the new world around it and transmitted the results of the measurements to Cassini, just as planned.
Then, 72 minutes after touchdown, the mother probe Cassini, which sent off Huygens days ago, disappeared behind the horizon. The landing module was now completely alone. Radio telescopes on Earth would continue to receive its carrier signal for a while longer, but it could neither send nor receive data now. Huygens’ main computer was programmed to continue its monitoring routine until the batteries were completely exhausted. A quarter of an hour later, the heat sensor recorded new data. The sensor consisted of a platinum wire; it sensed a change of electrical resistance. This meant the temperature at the base of Huygens must have increased.
The computer was not supposed to interpret this event. However, its programming was flexible enough to react to unexpected occurrences. The software increased the sensitivity of other sensors in the SSP, or Surface Science Package. The Acoustic Properties Instrument (API) measured how fast sound was propagating. The Refractive Index Sensor (REF) determined the refractive index of light. The Fluid Permittivity Sensor (PER) examined the propagation of magnetic fields. All instruments agreed the properties of the soil must have changed. Had the heat on the underside of Huygens caused the ice crystals underneath it to melt? That should not worry the lander. It was able to float, as its designers wanted to be prepared for an ocean landing.