Deep space exploration

{{Short description|Branch of astronomy}}

File:NASA's Deep Space Antenna Upgrade to Affect Voyager.jpg's Canberra facility in Australia]]

Deep-space exploration is the branch of astronomy, astronautics, and space technology that is involved with exploring the distant regions of outer space.{{cite web |url=http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html |title=Space and its Exploration: How Space is Explored |work=NASA.gov |access-date=2009-07-01 |url-status=dead |archive-url=https://web.archive.org/web/20090702153058/http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html |archive-date=2009-07-02 }} However, little consensus has been reached on the meaning of "distant" regions. In some contexts, it is used to refer to interstellar space. The International Telecommunication Union defines deep space to start at a distance of {{convert|2|e6km|e6mi|abbr=unit}} (about 0.01 AU) from Earth's surface. NASA's Deep Space Network has variously used criteria of {{cvt|16,000|–|32,000|km|mi}} from Earth. Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

At present the farthest space probe humankind has constructed and launched from Earth is Voyager 1, which was announced on December 5, 2011,{{cite web |url=http://voyager.jpl.nasa.gov/news/new_region.html |title=Voyager - the Interstellar Mission |access-date=2011-12-19 |url-status=dead |archive-url=https://web.archive.org/web/20120106063528/http://voyager.jpl.nasa.gov/news/new_region.html |archive-date=2012-01-06 }} to have reached the outer edge of the Solar System,{{cite web |url=http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980224b.html |title=The Farthest Spacecraft |work=NASA.gov |date=1998-02-24 |access-date=2009-07-01 |archive-date=2014-01-07 |archive-url=https://web.archive.org/web/20140107234524/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980224b.html |url-status=dead }} and entered interstellar space on August 25, 2012.{{cite web |url=http://www.aaas.org/news/releases/2013/0912_voyager-heliosphere.shtml |first=Brandon |last=Bryn |title=Voyager 1 Now Probing Unexplored Region of Space |work=Science |date=2013-09-12}} Deep space exploration further than this vessel's capacity is not yet possible due to limitations in the propulsion technology currently available.

Some of the best candidates for future deep space engine technologies include nuclear fusion propulsion, laser/maser propulsion, and antimatter.{{cite conference|url=https://ntrs.nasa.gov/api/citations/20200000759/downloads/20200000759.pdf |title=Prospects for interstellar propulsion |publisher=NASA |conference=Annual AAS Guidance, Navigation and Control Conference|access-date=2024-05-16|first1=Ronald J|last1=Litchford|first2=Jeffrey A|last2=Sheehy}} The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.{{cite journal |title=Ad Astra! |journal=Journal of the British Interplanetary Society |first=Robert L |last=Forward |volume=49 |pages=23–32 |date=January 1996 |bibcode = 1996JBIS...49...23F }}