# Internet of Spacecraft for Multi-Planetary Defense and Prosperity
## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **Type** & **Example** & **Launch Year** & **Program Entity** & **Status** & **Feature** \\ \hline  & & & & & first flybys of Jupiter, \\  & & Voyager 1 & 1977 & USA & traveling & Saturn and Titan; \\  & & & & & & Furthest and first \\  & & & & & & interstellar spacecraft \\ \hline planetary & Cassini- & & & USA/ESA/ & & first Saturn orbiter \\ probe & Huygens [5] & 1997 & Italy & finished & & and moons flybys; \\  & & & & & Huygens probe landed \\  & & & & & on Titan, first (non- \\  & & & & Earth) moon landing \\ \cline{2-5}  & New Horizons & 2006 & USA & continued & first Pluto flyby \\ \hline comet probe & Rosetta [6] & 2004 & ESA & deorbited & first comet landing \\ \hline planetary & Double Asteroid & & & & first kind for testing a \\ defense & Redirection Test & 2021 & USA/ESA/ & traveling & & method against near- \\  & (DART) [7] & & Italy/Japan & & Earth objects (NEO) \\ \hline \end{tabular}  
* the European Space Agency and it consists of 22 countries.  
\end{table} 
Table 1: _Cont._Furthermore, more uncrewed spacecraft have been launched, including various types such as Earth-orbit satellites, lunar/solar probes, planetary probes, comet probes, and asteroid probes (for planetary defense). The Hubble Space Telescope (HST) shown in Figure 3a is a space telescope launched into the LEO in 1990 and is still in operation. It features a 2.4-m mirror and is located at a variable altitude of around 537 to 540.9 km, with five main instruments to observe in the ultraviolet (UV), visible, and near-infrared regions of the electromagnetic spectrum. Many Hubble observations have led to breakthroughs in astrophysics [10, 11], e.g., it assisted scientists to determine the expansion rate of the universe and resulted in the Nobel Prizes in 2011. Its end of mission is estimated to be around 2030-2040, while its successor, the James Webb Space Telescope (JWST) illustrated in Figure 3b was launched on 25 December 2021, and is supposed to be in the orbit of Sun-Earth L\({}_{2}\)[12, 13], the second Lagrange point. Figure 1: (**a**) Apollo 11 lunar module Eagle and astronaut [PERSON] on the Tranquility Base of the Moon on 20 July 1969 [1]; and (**b**) the view of ISS exterior and steelwork from the departing SpaceX Crew-2 spacecraft on 8 November 2021 [3]. Figure 2: (**a**) The SpaceX Crew Dragon spacecraft docked to the ISS in 2021 [2]; and (**b**) Starship Serial Number (SN) 9 sitting on its launch pad in Starbase [9]. On the other hand, the planetary probes have been under the spotlight these years, and many nations have joined the race of sending probes to other planets. The recent operational Mars probes include Perseverance from the USA in 2020, Tianwen-1 from China, and Hope from the United Arab Emirates (UAE). One of the earliest pioneering spacecraft of this type is Voyager 1, launched in September 1977. As of November 2021, it has already traveled 155.5 astronomical units (AU) (23.26 billion km), which is currently out of the heliosphere and has become the first interstellar spacecraft and most distant artificial object from Earth. The Cassini-Huygens spacecraft is a collaboration among NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to study the planet Saturn and its system, including its rings and natural satellites. It consists of the Cassini space probe and ESA's Huygens lander, which landed on Saturn's largest moon, Titan, in January 2005. An illustration is presented in Figure 4a. NASA had conducted the mission extension after 2008 until September 2017 when Cassini was intentionally sent into Saturn's atmosphere to be destroyed to prevent biological contamination. Many astonishing scientific discoveries have been reported from its 20-year journey in space, which include the observation and analysis of Enceladus' water vapor plume [15,16] and tests of [PERSON]'s general theory of relativity [17].