Making Changes Too Soon!
Generally NASA spacecraft and rovers (and now helicopters) are designed with plenty of margin in their critical systems to assure that the Primary Mission is completed with as low a risk of failure as is reasonable.?
Q: What happens when a NASA Science mission successfully completes its primary mission???
A: One thing is certain, they don’t get turned off! NASA hosts a Senior Review to consider extended objectives for the mission until either the systems give out or all the science that can be done is.?
A Senior Review is a stressful time for a mission science team as often the careers of the rising scientists depend on these extensions to develop and explore new facets to the science.?
Here are a few famous extensions:
Voyager 1 & 2 (43 years in extensions)
???Launched 16 days apart in August and September of 1977, these amazing space probes had a primary mission to explore our solar system out to Saturn (9.5 AU* away!). Their Primary Missions ended in 1980 and 1981. They are still operating today, and are the furthest human made objects from the Earth. Voyager 1 is 156 AU away. Voyager 1 entered interstellar space in 2012 and Voyager 2 in 2018.
*1 AU = 93 million miles (the distance from the Sun to the Earth)
Mars Exploration Rovers, Spirit & Opportunity (6 & 15 years in extensions)
???Launched in July of 2003 and landed on Mars in January 2004, the rovers were expected to last 90 days.??Spirit lasted till 2010 and Opportunity till 2019. The first mobile missions on Mars (not including Pathfinder), these rovers enabled scientists to get up close to the surface of Mars and begin to understand the geology there, and at the same time endeared themselves to the public.?
Cassini (13 years in extensions)
???Launched in October of 1997 the spacecraft took over 6 years to reach Saturn. Its Primary Mission at Saturn was 3 years long and planned to end in 2007. NASA ultimately terminated the mission after over 13 years at Saturn by sending it dramatically beneath Saturn’s rings and into the planet's upper atmosphere. Even in its last breath, Cassini was exploring and enabling new science.
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Hubble Space Telescope (33 years old, so far)
????Launched in April of 1990, HST overcame some initial challenges, has been serviced 5 times and is expected to last until 2030 at the earliest. In the course of its lifetime, HST and its data have changed text books, challenged scientific thought and inspired the public.
New Horizons (7 years in extensions, so far)
????Launched in 2006, the Pluto-Kuiper Belt explorer arrived at Pluto in 2015. Its Primary Mission was set to end in October 2016. Now 7 years later and 55 AU away, the probe has entered the Kuiper Belt with a suite of instruments still operating set to explore an unknown region of our Solar System, which has recently been speculated to actually be two belts!
It’s unusual, but not without precedent, to repurpose a spacecraft to support a different scientific mission and to repopulate the science team with different scientists… AFTER it has finished its original purpose. As an example, the Voyagers were transitioned from Planetary Science missions into Heliophysics** missions after they left Saturn.?
** Heliophysics is the study of the Sun and its connection to the solar system.
Even though during the last Senior Review New Horizons received high marks for the proposed extended mission science, NASA management is considering an early transition of New Horizons into a heliophysics science mission which would, by default, replace the current science team. Ultimately this will happen but, in the opinion of many colleagues (and myself) in an open letter to NASA, this transition is premature. New Horizons hasn’t exhausted the Planetary Science that could be done inside the Kuiper Belt. Repurposing it before it exits the Kuiper Belt means releasing a science team, some of whom, have been with the mission since before launch in 2006.?
New Horizons will eventually get beyond the Kuiper Belt and into interstellar space (just like the Voyagers), but now is not the time to interrupt the progress through the Kuiper Belt (or possibly “Belts”). NASA should hold off the repurposing of this iconic space probe for the next 5 years. Instead they should lean forward into an opportunity to explore and while finishing the traverse of the Kuiper Belt they can begin adding Heliophysicists to the science team who can prepare for the probe’s (eventual) new chapter.
Keith Cowing has posted the open letter a number of us signed here:
I appreciate the advice and edits of both Dr Alan Stern and Dr Jim Green as this piece was in final edit.
Alan Stern , has been the Principal Investigator of the New Horizons mission since it was first conceived in 2000 in partnership with the Johns Hopkins University Applied Physics Lab.
James Green , is the former NASA Chief Scientist and Director of NASA's Planetary Science Division.
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1 年Jim, you always have, and always will impress me with your passion and professionalism!