New Horizons

New Horizons is a NASA spacecraft that will explore the dwarf planet Pluto, its moon Charon, and possibly providing two additional 2005 newly discovered smaller moons named Nix and Hydra as part of the New Frontiers program. In the years 2011 and 2012, the even smaller moons Kerberos and Styx were found to be possibly also investigated. New Horizons is the first space probe, which will enable astronomers to explore Pluto up close. It is planned to watch the world go at 9600 km distance to Pluto and Charon at 27,000 kilometers distance the probe in July 2015.

The probe was launched on 19 January 2006 at 19:00 UTC clock aboard an Atlas V ( 551 ) rocket. After a swing-by maneuver past the Jupiter, which took place on 28 February 2007, they will reach their destination on 14 July 2015 and eventually penetrate further into the Kuiper belt. Currently (April 8, 2014), the probe is approximately 29.044 AU from the Sun, about 29 AU from the Earth and still about 3.684 AU from Pluto away.

The project is led by the Applied Physics Laboratory of Johns Hopkins University in Baltimore, Maryland, USA. The cost, including the development and construction of the spacecraft and its instruments, the launch vehicle and mission execution in 2016 amounted to about 700 million dollars.

  • 4.1 Start
  • 4.2 On the way to Jupiter
  • 4.3 flyby of Jupiter
  • 4.4 Pluto and the Kuiper Belt

Mission Objectives

Pluto has been visited by any spacecraft. Since he is very far away from the sun, even the most powerful telescopes can barely make out details on its surface. Thus, the resolution of the best recordings obtained with the Hubble Space Telescope reached only 500 km per pixel. Thus, Pluto and its moons are extensively studied only by space probes. NASA divided the mission objectives of the probe in three priority categories, depending on what the scientists want to find out about Pluto and Charon (since the since discovered moons at the time were unknown, they are not considered here ):

  • Outline of the overall geological structure and geomorphology of Pluto and Charon
  • Mapping the composition of the surfaces of Pluto and Charon
  • Description of the neutral (non- ionized ) atmosphere of Pluto and its escape rate
  • Description of the time-dependent variability of the surface and atmosphere of Pluto
  • Stereo images of Pluto and Charon
  • Mapping of the day-night boundaries ( terminator) of Pluto and Charon in high resolution
  • Mapping of selected surface areas of Pluto and Charon in high resolution
  • Description of the ionosphere Pluto and its interaction with the solar wind
  • Search for specific chemical compounds such as hydrogen, hydrogen cyanide, hydrocarbons and nitriles in the upper atmosphere of Pluto
  • Search for an atmosphere of Charon
  • Determination of bolometric luminosities and from the geometric albedo of Pluto and Charon
  • Mapping of the surface temperatures of Pluto and Charon
  • Description of high-energy particles in the vicinity of Pluto and Charon
  • Refinement of the parameters ( radii, masses, densities ) and orbits of Pluto and Charon
  • Search for magnetic fields in Pluto and Charon
  • Search for planets rings and other moons

NASA defines the mission of New Horizons as successful if all necessary classified as goals are achieved. With the help of its seven instruments the probe is to achieve all the objectives of all priority categories and therefore may exceed these requirements by far.

In addition, the exploration of Jupiter to the mission objectives at which flew past the probe in February and March 2007 belonged. Cloud motions were observed, it was the magnetosphere of the planet investigated and held out for auroras and lightning in Jupiter's atmosphere. However, only a limited number of scientific data could be obtained via the four large Galilean moons, because the probe happened this in a relatively large distance.

Should the funding of scientific operation of the spacecraft be secured through the 2016 primary mission ended addition, one or more objects can be approached and studied in the Kuiper Belt.


The spacecraft is about the size of a grand piano and a triangular shape with a cylindrical radioisotope generator ( RTG), which is attached to a tip of the triangle. In addition, it has a 2.1 m parabolic antenna for communicating with the ground, which is fixed to one side of the triangle. The dimensions of the probe body without the RTG and without the antenna are: 0.7 m high, 2.1 m long and 2.7 m at the widest point. The overall height of the payload adapter to the upper end of the antenna is 2.2 m. The total mass of 77 kg, including fuel and 30 kg scientific payload is 478 kg. On a flight without a swing-by at Jupiter, the initial weight of the probe would have less situated at about 20 kg. The difference, however, would have affected only the amount of fuel carried and results from the fact that the launcher has to reach higher top speed with a direct start to Pluto and can carry less payload. The original plan foresaw a launch mass of vollbetankten probe of 465 kg after the verification of the performance of the new Atlas V launch vehicle by previous starts off mass could be slightly enlarged.

The supporting structure of the probe consists of a central aluminum cylinder, which houses the fuel tank made ​​of titanium and acts as an adapter between the sensor payload and launch vehicle interface as well as between the probe and the RTG. The RTG is mounted by means of a four-sided titanium base of the spacecraft. In order to keep the mass of the probe low, the panels of the probe body made ​​from aluminum sandwich construction with very thin frontal plates are made ( as thick as two sheets of paper). Electronics and instruments are grouped around the cylinder, the arrangement of the systems had to take on the center of gravity into consideration.

New horizons can be used both as a three -axis stabilized operated spin stabilized. Three-axis stabilization is applied and system testing instrument during scientific observations and spin stabilization (usually with five revolutions per minute) during the course correction maneuvers during long radio contact with the ground and during the flight periods. In order to allow Spin stabilization during flight, the probe was balanced before the start of accurately measured and additionally attached balancing weights.

There is some ashes of Clyde Tombaugh, who discovered Pluto in 1930 on board of New Horizons. The spacecraft also carries a CD, which is described with 430,000 names of Internet users who had registered on the New Horizons website for the "Send -Your- Name -to- Pluto " action.

Energy supply

The probe is powered by a container filled with about 10.9 kg of plutonium 238Pu radioisotope generator (RTG ) of the model GPHS - RTG with energy. The RTG contains 18 modules, each containing four capsules each with 151 grams of plutonium in the form of plutonium dioxide ( PuO2 ). The capsules were at Los Alamos National Laboratory of the U.S. Department of Energy (DOE ) established.

Mid-2004 were all the work of Los Alamos National Laboratory, including at the plutonium for New Horizons, stopped, because it was found that some hard drives allegedly disappeared with secret information. This makes the whole project was in danger, because if an insufficient energy supply, the probe limited or no observations could perform. However, the security issues of the Los Alamos National Laboratory could be solved after some time, and the work on the plutonium capsules were resumed.

End of 2005, the RTG was delivered and installed in the probe. However, he probably contains less plutonium capsules than originally planned. It was intended that the performance of the generator at full load at startup plutonium 285 W and 225 W will be the Pluto flyby in 2015 ( road enters a lowering of the power due to the decay of plutonium a ). After the problems with the production DOE spoke of about 190 W of power during the flyby of Pluto. This would be for a normal operation of the probe on Pluto enough (at least 182 W is needed ) and the probe could even up to about the year 2025Vorlage: keep future / In 5 years functional. After the now completely built RTG tests underwent in October 2005, it turned out that the generator delivers even more energy than expected. It is now of about 240 W at the beginning of the mission and 200 watts of on reaching Pluto at a DC voltage of 30 volts. Typical of an RTG - powered mission New Horizons has no batteries.


New Horizons has two computer systems: the Command and Data Handling system for controlling the probe, and working with scientific data and the Guidance and Control System for position control. Each of the computer systems is duplicated for redundancy, so that the spacecraft has four separate computer systems. The on-board computer each use a Mongoose V processor. This is a 12 MHz fast, hardened against radiation version of the MIPS R3000 processor.

The Command and Data Handling system has two flash recorder with 8 GB (64 Gb ) memory to cache the gained during the operation of the instruments scientific data before it can be transmitted to Earth.

To save space and weight, the electronics of the spacecraft and the interfaces to their electronic instruments are housed in an " Integrated Electronics Module" ( IEM). There are two redundant IEM on board.


The communication system of the spacecraft is operating in X-band and has a 2.1 m parabolic high-gain antenna ( High Gain Antenna - HGA ) with an opening angle of 0.3 degrees, a 30 - cm mid -gain antenna (Medium Gain Antenna - MGA ) with an opening angle of 14 degrees and two omni-directional antennas with low gain ( low Gain antenna - LGA), which are located on opposite sides of the spacecraft. All antennas are firmly attached to the probe body. The HGA and MGA antennas of the probe must be aligned to the earth to use as they can. The probe has two redundant 12 -watt traveling wave tube amplifiers that are mounted under the HGA.

The high-gain antenna and the center -gain antenna be used for data transmission, the data transfer rate of the HGA to a 70 - m antenna of the Deep Space Network is near Pluto about 700 bits per second ( on Jupiter with 38 kbit per second). By comparison, the much older Voyager probes reached a similar distance still 1400 bits per second ( also at X-band ).

For the case that the probe can not be aligned on the ground, and these antennas are not available, the two omni-directional antennas (LGA ) of the probe can be used. This need not be aligned, but reach only very low data rates. However, since the probe has on opposite sides of two of these antennas, they can send and receive from all directions. They are used during takeoff and Communication in the vicinity of the earth, and to allow a secure communication in an emergency.

In order to reduce the operating costs of the probe, New Horizons will spend the flight distance between Jupiter and Pluto in a kind of "hibernation " ( hibernation mode). The probe is once " woken up" 50 days per year to perform functional tests and to determine accurate flight parameters. For the remainder of the probe is displaced in a slow rotation. It is only once per week send a signal to the ground whose frequency is indicative of either the normal operation of the probe, or one of the seven failure modes. This type of communication has been tested with Deep Space 1, New Horizons is the first space probe that they used in operational use.

Drive system

The propulsion system of the spacecraft is used only for course corrections and attitude control. It is not intended to accelerate after separation of the rocket upper stage, the probe strongly or decelerate, as would be necessary, for example, at a Orbiter mission. The drive system consists of engine 16, and catalytically decompose the hydrazine are mounted at eight different locations on the probe surface. Of deliver four larger engines, which are mostly used for course corrections, a boost of 4.4 Newton as well as 12 smaller engines have a thrust of 0.8 Newton. The smaller engines are used for alignment of the probe as well as initiating and stopping the rotation. Half of the 16 engines are spares.

The probe carries 77 kg of hydrazine on board, which would be enough to change the speed of the probe to about 400 m / s (1440 km / h) ( were minimal in the mission planning 290 m / s provided ). Most of this fuel is planning to use to after the passage of Pluto or one can control several Kuiper belt objects. To set the fuel under pressure, helium is used.

Navigation system

Navigation systems and sensors provide information about position, course and spatial orientation of the probe during the flight. These data are crucial in order to perform precise course correction maneuvers in order to align the instruments to the objectives and to the antenna on the earth can.

Go to navigation two redundant star trackers (Star Tracker ), Inertial Measurement Units ( IMU ) and sun sensors are used. The navigation data is processed by the Guidance and Control computer system which controls the position of the probe by the firing of the small engines. One of the star cameras makes ten times per second, a wide angle shot of the star background and compares it with a stored star map that contains 3000 stars. Thus, the exact orientation of the probe in both the three-axis - stabilized as well as spin-stabilized operation is determined. The IMU, which comprise gyroscopes and accelerometers which provide information about 100 times per second movement of the probe. The sun sensors are used the orientation of the probe to the sun (and therefore from a distance on the earth ) to ensure communication in the event of failure of other navigation systems. These sensors are very easy to set up and return the answer only if they do not see the sun or.

Temperature Control

New Horizons is designed so that the probe body can retain the heat generated by the electronics like a vacuum. With the great distance to the sun it is necessary to comply with temperatures of 10 to 30 ° C in the interior of the probe can. To this end, the probe body including the large antenna is provided with a lightweight gold-colored cover, which consists of 18 layers Dacrongewebe that lie between an aluminised Mylargewebe and a Kapton film. In addition to thermal insulation, this cover also serves the micrometeorite protection.

An automatic heating system monitors the energy consumption inside the probe to ensure that all the devices with enough power and therefore emit enough heat. If the energy consumption of less than about 150 watts, small heaters are turned on inside the probe to compensate for the difference in performance. If the probe is close to the earth and with it the sun, the temperatures can exceed safe levels. For this case, the probe has a kind of blind system ( " Louvre " ) with fins that are opened to radiate excess heat into space. In the closed state, the outer surface of the light lamellas for a low radiation provides.


The probe carries seven scientific instruments, which are described below. Here, some of the instruments are grouped together: as Pluto Exploration Remote Sensing Investigation ( PERSI ) contains the instruments Ralph and Alice and Particle Spectrometer suite (PAM ) the instruments SWAP and PEPSSI. The instruments together weigh approximately 30 kg and consume together something under 28 watts of electrical power.

Functioning of the mission

Since the early 1990s, there were attempts to launch such a mission to Pluto. Priority was about to reach Pluto before its thin atmosphere freezes out, because the orbit of the dwarf planet is highly eccentric, and Pluto reached the point nearest the Sun its orbit ( perihelion ) in 1989 ( this earlier assumption that the atmosphere after the passage of the sun nearer track region would freeze out soon, could not be confirmed so far ). Currently, he moves away from the Sun, so it is always colder on Pluto; only in the year 2247 he will play his next perihelion. The first concepts of a mission but (Pluto Fast Fly-By, Pluto Kuiper Express) failed due to technical and financial difficulties. The end of 2000 there were with New Horizons a new proposal for a Pluto mission. Finally, this proposal has been approved as the first mission of the newly created New Frontiers program for realizing on 29 November 2001.

The instruments of the probe were delivered between July 2004 and March 2005, assembling and testing ran from August 2004 to May 2005. From May to September 2005, the ready -built probe was tested extensively, on 24 September 2005 was the transport to Cape Canaveral.

The end of October in Cape Canaveral damaged by Hurricane Wilma a solid rocket boosters of the almost fully assembled Atlas V launch vehicle for the New Horizons, as a goal of the assembly hall did not withstand the wind pressure. However, the booster could be exchanged in time before the scheduled start date on 11 January 2006.

On 16 December 2005, NASA ordered an additional evaluation of the first stage tanks, because at a pressure load test another Atlas rocket this stage the required maximum load had not withstood. Thus, the amount recognized for the January 11 launch date six days there was a shift to the 17 January 2006.


The launch window opened on 11 January 2006 and remained until February 14, 2006,. However, there was the possibility of a flyby ( swing-by maneuver) on Jupiter only at a start up to and including February 2. Then you could reach the Pluto system only on a direct path, which extends the flight time by several years and the amount of fuel could be carried along reduced by 20 kg.

After the scheduled start on 17 January 2006 due to strong wind, had to be postponed several times, New Horizons should start on 18 January 2006. Due to a power outage in the ground station of the Johns Hopkins University could not be held this appointment. On January 19, New Horizons was launched after several postponements due to dense cloud cover finally at 19:00 UTC clock ( the launch window was from 18:07 bis 20:07 clock UTC open) of Launch Complex 41 after 44 minutes and 55 seconds, the probe was suspended by the missile in its final trajectory.

The launch took place with an Atlas V ( 551 ) rocket. Although this rocket was the most active launch vehicle in the world at this time, the payload had to be equipped with an additional Star -48B - stage in order to speed up the probe to a high velocity well above the escape velocity can. New Horizons left Earth with the highest ever achieved thereby speed of 16.21 km / s On other days of the start window, the speed would have been somewhat different, especially after February 2, without the possibility of a flyby of Jupiter, the speed of the lighter then the probe should have been much higher.

If the probe has not been started in 2006, there would have been another launch window between February 2, 2007, and February 15, 2007, but the only direct flight would also be allowed to Pluto, with the negative consequences.

On the way to Jupiter

One day after the start was the high rotation of the probe, in which it has been displaced from the upper stage rocket, reduced from 68 to 19.2 revolutions per minute. On January 22, the rotation was further reduced to five revolutions per minute, and the star trackers were put into operation.

On 28 January 2006, the first course correction was performed (TCM -1A ), the thrusters fired for about five minutes. Two days later the next twelve -minute course correction (TCM -1B ). The two course corrections resulted in a change in velocity of 18 m / s Another course correction (TCM -2) was planned for 15 February, but was canceled. The next, 76 -second course correction (TCM -3) on 9 March and was the first to be carried out in the three -axis stabilized mode. The speed of the probe was changed s to 1.16 m / Through TCM -3.

In February, the protective shutter of Alice spectrometer was opened, and on March 13, followed the SWAP instrument. Also in March, the SDC experiment was activated. By 29 March, all instruments had completed their internal electronic checks. On 7 April 2006, the probe crossed after 78 days of flight time, the orbit of the planet Mars. In May, the protective shutters of the instruments PEPSSI (May 3 ), Alice (May 20 ) and Ralph (May 29 ) were opened. In summer, the calibration experiments were carried out.

Early May 2006, the researchers found that New Horizons will on the way through the asteroid belt the three to five kilometers large asteroid ( 132524 ) APL approach. The probe came on 13 June 2006 at 04:05 UTC up to 101,867 km on the asteroid approach. Since the protective shutter of the high resolution camera LORRI was not open due to the small distance to the sun (which was open until 29 August 2006), the visual observations were made only with the weaker Ralph instrument. This could resolve the asteroid only as an object of one to two pixels size.

On September 4 New Horizons took on her first image of Jupiter. This was produced by the LORRI camera, the distance to the giant planet was at the time of recording 291 million kilometers. Other instruments observed Jupiter, primarily for the purpose of calibration.

Flyby of Jupiter

The first scientifically relevant studies of the Jovian system began in January 2007 and lasted until the end of June 2007. It was planned about 700 observations and measurements of the gas planet, its moons and its magnetosphere.

On February 28, 2007 New Horizons flew by Jupiter, the smallest distance to the giant planets was reached at 05:43 UTC clock and was about 2.3 million kilometers (about 32 Jupiter radii ). This is a third of the distance at which the Saturn probe Cassini -Huygens passed the Jupiter. The trajectory of New Horizons was just outside the orbit of Callisto, the outermost of the four Galilean moons. During the flyby, the probe photographs of Jupiter, its rings and the four Galilean moons made ​​of, as well as measurements of the magnetic field were carried out. Through the flyby, the probe experienced an increase in speed of 3890 m / s and was redirected to a trajectory to Pluto, where it was thrown out by about 2.5 ° from the ecliptic.

Pluto and the Kuiper Belt

On June 8, 2008 New Horizons crossed the orbit of Saturn, but remained far from him. On 30 June 2010, a course correction was performed and enhanced by a boost pulse duration of 36 seconds, the speed of the probe to about 0.45 m / s to compensate for the deceleration by backscattered from the HGA thermal radiation. On March 18, 2011, 23 clock, the probe reached the orbit of Uranus, the gas giant was more than 3.8 billion kilometers away at this time and therefore no observations were made. On August 25, 2014, the orbit of Neptune is to be achieved, exactly 25 years after the flyby of Voyager 2 to Neptune. Also Neptune is then far from New Horizons removed in order to perform meaningful observations of the planet can.

However, be on the way to Pluto probably Neptune Trojans that get close enough to the probe was observed.

On 15 July 2015, the probe will reach Pluto. The observations of the Pluto -Charon system start about 150 days before the closest approach. About 120 days before the flyby, the first pictures are expected, and 90 days before the flyby will be surpassed by the images of the LORRI camera, the best resolution of the Hubble telescope. There are global maps of Pluto and Charon, won high resolution photos of up to 25 m per pixel resolution, measured the temperature distribution and the atmosphere of Pluto are studied. It is planned to allow the probe to fly past at 9600 km distance to Pluto and Charon at 27,000 kilometers distance. However, these are only objective parameters that can be changed during the flight easily. Two weeks after the flyby, the observations are completed, and the probe will begin to transmit the data collected during the flyby to Earth. Since the transmission rate over this distance is very small, a few months will pass before all data has arrived on Earth.

After the flyby of Pluto, the probe will continue their journey out of the solar system beyond while flying through the Kuiper belt, where between 2016Vorlage: Future / In 2 years and 2020Vorlage: Future / In 5 years flybys of one or two Kuiper belt objects with a size are possible from an average of 40 to 90 km in diameter. However, the precise objectives for first have to be found and are likely defined between 2013 and 2014. The sequence of observations for these objects should be similar to the observation of Pluto, however, limited by the decreases in the level of sunlight, the energy of the probe is available and the data transfer rate. It is estimated that the probe is to have enough energy to about 2025 available to carry out observations of these objects.

Project IceHunters

Search within the framework of the Citizen Science project IceHunters volunteers in their spare time for objects in the Kuiper Belt to find a successor goal for New Horizons. To this end, they analyze images obtained from the subtraction of recorded at time intervals astronomical images. Astronomical knowledge is not necessary for this activity.