NASA’s New Horizons spacecraft has brought joy and wonder to both children and adults alike with images from Pluto and a Kuiper Belt object beyond it. However, an unexpected proposal could undermine its future – something the public deserves to know about.
New Horizons currently rests between Jupiter and Pluto, emerging once every year for equipment checks and trajectory tracking as well as exploring its local region by monitoring collisions of dust particles within it.
Attitude control is used to maintain and adjust the orientation of a spacecraft in space. Sensors detect any changes to body posture of the spacecraft, then generate corrective torques which are sent via command signals back to Earth for application on-board the spacecraft.
New Horizons was fully fuelled when launched, weighing 478 kilograms (1,054 pounds). Its dimensions approximate those of a piano. New Horizons uses only one radioisotope thermoelectric generator to power its systems and seven science instruments – requiring less energy than required to light two 100-watt light bulbs!
New Horizons was developed and integrated at Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland with contributions from NASA Goddard Space Flight Center, Southwest Research Institute and other institutions. It features an aluminum central cylinder which houses instrumentation as well as interfaces with its rocket-powered launch vehicle. Internal and external panels serve as mounting points for its many subsystems; in addition to passive spin stabilization system REX features an advanced, highly redundant Command and Data Handling (C&DH) and Communication System which features REX radio science experiment.
An optimally functioning spacecraft must be precisely aligned in order to collect data with instruments, communicate with Earth and navigate space. New Horizons relies on onboard gyros, star trackers and sun sensors in order to accurately locate its position in space.
Star trackers capture images of the starry skies every second and compare them against a database of known stars to pinpoint where the spacecraft should be oriented in its orientation frame. Sun sensors provide redundancy to star trackers by only detecting sunlight; helping with attitude acquisition.
New Horizons utilizes a navigation suite composed of star trackers, sun sensors and gyroscopes in combination with star sensors to calculate solar, Earth and Pluto vectors that allow it to point its antennas and instrument beams during various mission stages. To save power consumption and protect batteries, this system employs innovative digital systems that reduce image transmission rates from spacecraft while performing lossless image compression on downlink data transmissions. Furthermore, an intelligent heating system monitors power levels to ensure safe temperatures are maintained by activating louvers when necessary.
Solar power is a primary energy source for spacecraft. To take full advantage of it, precise solar pointing must be achieved. Sun sensors support this ability from launch through save mode and flight.
Sun sensors detect sunlight passing through windows and generate current proportional to its intensity, enabling one to determine its two-dimensional vector.
New Horizons utilizes a dual-redundant star tracker with sun sensors to precisely determine its orientation in space and minimize body rates during science sequences at Jupiter and Pluto. Many of these sensors originated on APL’s CONTOUR and Ulysses missions.
At TNO, a radiation hardened digital sun sensor with multi-spot design has been created to enable precise sun-line determination. Featuring 2 measurement axes and 5 sensors, this versatile instrument comes in various configurations from coarse to fine ranging in resolution.
New Horizons’ structure is comprised of a triangular prism composed of titanium and sandwich panels with ultra-thin aluminum face sheets adhered to an aluminum honeycomb core, offering maximum stability while remaining light enough for easy navigation towards Earth, Pluto, or any other desired science target.
A sophisticated power system keeps an eye on electronics to ensure they consume enough wattage to maintain safe thermal margins, and if this level falls below it sends out an alert with instructions to activate heaters as soon as possible.
New Horizons was engineered to retain heat like a thermos bottle. The vehicle is covered with multilayered thermal insulation reminiscent of survival camping blankets to hold in heat produced by operating systems and the OSB sheathing layer that is susceptible to moisture damage. To prevent overheating, electronic activity is limited while louvers open to shed excess heat; additionally a shunt regulator reroutes excess RTG power via electric heaters which keeps New Horizons safe operating state through Jupiter flybys, Pluto encounters and an Arrokoth Kuiper belt encounter.