For millennia, Kerbals gazed in wonder at their night sky. Early societies had a fascination with the movement and location of the celestial bodies, and studied them in great detail. They noticed how some points of light traveled across the night sky, and attributed mythological significance to them. These points of light, the planets, were recorded as they progressed along their paths across the night sky; complex sky charts were developed. As time and technology progressed the Kerbals studied these further and in greater detail. They realized and calculated that they must be quite close to Kerbin and perhaps orbited it or orbited the Sun. One of these points of light traveled far slower than the others. It was calculated that this planet must be much farther away. The invention of the telescope revolutionized their study of the planets. Its inventor, Jebileo Kerman, had a particular interest in this distant planet. One night, peering at it through his telescope, he discovered that it was orbited by other worlds, its moons. He described the planet as a “beautiful jewel, which graces the night sky as it passes by.” Through an act of accidental misspelling on Jebileo’s part, this planet was named “Jool”, and the name stuck. Though the planets were of great interest to Kerbals, they were limited in their ability to study them because of the basic technology of the time. Jool’s secrets continued to remained hidden.
The advent of the space age enabled Kerbals to study the planets in much greater detail and depth. Probes to the planets could perform a wide array of studies and observations, and could relay fantastic images back to Kerbin. Through much of the early space age, however, limited technology and inexperience forced the Kerbals to send missions to only the inner worlds. A number of probes sent to Kerbin’s moon and the inner terrestrial planets of Eve and Duna were successful, and these probes studied them extensively. As technology progressed, scientists turned their eyes towards Jool. A program was drawn up and designed for the spacecraft study of Jool. This program, aptly named Project JOOL, would hopefully enable scientists to unlock the mysteries the giant gassy outer world held and help them build a better understanding of the Kerbin solar system. JOOL, which stood for Jool Orbit Observation and Landing, was both the name of the world the program intended to study and the main goals of its designers. They hoped to study and photograph the planet and its moons in great detail. Space probes would be placed into orbit around the planet and possibly one of its moons. Eventually, a probe would be sent which would carry and deploy a lander which would land on one of these moons. Soon after the program was announced, work went underway.
PART 1: The JEFF (Jool Encounter First Flyby) Mission
Though it would take years for the more complex missions to be designed and developed, the first spacecraft sent to Jool took flight soon after the JOOL program was announced. In many ways, it was a precursor mission to the later ones. The probe was not actually designed or constructed for a mission to Jool. Instead, it had been a leftover 1.74 ton probe from early in the program to study Eve which was refitted and commissioned as a Jool probe. It had a basic and limited camera, but carried a number of instruments which could take complex measurements of the planet and space around it. It was intended that the probe intercept and fly past Jool, taking pictures of the planet and its moons and making measurements as it passed. It would then likely be flung out of the solar system.
Opposite side of the JEFF probe. On the right are batteries, on the left is the computer guidance device and a small electrical generator.
JEFF was launched from the Kerbal Space Center aboard a Warrior II-H Launch Vehicle at 11:25 pm. The launch vehicle and launch configuration was essentially the same as what it had been the case for the EVE missions. The launch went perfectly, and the Warrior II-H performed better than had been expected. JEFF was placed into a orbit of 90 km around Kerbin. It spent 11 days in orbit around the planet, during which time flight controllers ran checks to make sure all systems were nominal.
11 days, 3 hours. and 6 minutes into flight, the rocket sprung to life and boosted the probe out of Kerbin orbit. The first stage’s fuel burnt through and was detached from the craft, and the second stage carried the craft towards Jool during a burn of 35 seconds.The launch vehicle lifting the probe into orbit around Kerbin. The second stage ignites, sending JEFF towards Jool.
As the probe left Kerbin’s sphere of influence, flight controllers turned it around and made it take pictures of Kerbin. These images demonstrated the probe’s imaging capabilities for the Jool flyby and also provided a fantastic look at the Kerbin-Mun system. The spacecraft now begun its long journey. 187 days later, the upper stage rocket relit and burnt for 5 seconds, placing the probe into a lower flyby altitude.
274 days after launch, the JEFF probe entered Jool’s gravitational sphere of influence. As it did, the probe oriented itself towards Jool and turned its instruments online. It began to continuously take photographs and stream them back to Kerbin. It approached Jool and took measurements and readings of its magnetic sphere, atmosphere, and gravitational pull. The moons orbiting it were also imaged and studied for the first time. The innermost moon, Laythe, was revealed to be a world with an atmosphere and an ocean. Tylo, the third moon, was measured to be as big as Moho, the innermost planet.
Laythe and Tylo imaged and studied.
The craft flew past Jool at a closest altitude of 250,000 km, and then was launched into a trajectory that would take it out of the solar system. As it left, it imaged the slowly receding Jool. The data collected by JEFF was invaluable for scientists back at Kerbin. A number of small moons were discovered orbiting Jool from a farther distance. The atmosphere of Jool was studied and reveled to be 138,000 km thick with a pressure of 15 atm. The photos that JEFF took were the first photos of Jool and its moon ever, and provided scientists with a trove of data and information about the Jool system. JEFF also demonstrated that it was entirely possible to send a complex probe as far as Jool successfully and receive adequate data. The experience gained from the flight was incredibly helpful to the scientists designing the plans and probes for the subsequent JOOL program missions.Jool receding into the darkness of space.