This article probes the conjunctural evolution of planetary missions and tries to explain the scientific and historical motives for Pluto and Kuiper Belt being the next target. And hereby we aim to track the path to accomplishment towards the New Horizons Mission.
This is the first article of the series: “New Horizons Mission – Its History, Route, Success and Future“.
The list of article series is as follows and the links for the next articles will be here once they are published.
- New Horizons Mission – Historical Background
- New Horizons Mission Goals
- New Horizons Spacecraft
- New Horizons Mission From Launching to Pluto Encounter
- New Horizons Pluto Flyby
- New Horizons Kuiper Belt and Ultima Thule Flyby
The New Horizons Legend – An Epic Journey to Kuiper Belt
The ultimate aim of the grand New Horizons Mission was a close flyby near Pluto System and exploration of one or more Kuiper Belt Objects. While New Horizons Spacecraft successfully performed its duty about Pluto and its secondary target, it is heading towards new targets in far worlds in the outer regions of Solar System.
Beginning with mid 2015, phenomenal images of Pluto and Pluto moons were publicized; and a slack bombardment of spectral data flow was initiated. This was followed up with evaluation and interpretation of those collections, and researchers are still working on the data to be able to explore and explain more. In the meanwhile, spacecraft continued its journey, took a glance to the next target Ultima Thule and moving on in Kuiper Belt.
This epic journey did not only explore Pluto System and Kuiper Belt, but also created a tremendous amount of inspiration to many, as well as Plutopic. We keep following New Horizons’ footsteps. And we are excited to see how it widens our horizons. New Horizons’ Spirit, in every aspect, is the one carrying the torch and bringing us together here!
Before New Horizons Mission – A True Story of Patience and Dedication
After 1970’s and especially for the space missions to outer planets, USA and NASA have been carrying the flag. And that makes it easier to track the historical events leading to a Pluto mission and its motives.
Decision of sending a spacecraft to billions of kilometers away is not an easy one. In fact, the process of “maturing” and “justifying” the ideas of such a “mission to a new world” can take decades. And some extra “lobbying” effort might be necessary for making the dreams come true.
Above is an ordinary story and easily applies to Pluto reconnaissance project discussions in USA till 2001!
Nonetheless, leading ideas for such a journey to Pluto were seeded long before NASA approved New Horizons project in 2001: This was a developing idea from discovery of Pluto to 1989!
It all began with secret organizations located underground, having their own hidden agendas..
Above might be a joke. But what’s not a joke is, in May 1989 a group of scientists including Alan Stern were sitting in an Italian restaurant in Baltimore. An “under the table” decision was made: Promoting Pluto missions in an organized way.
For that goal, they formed a group and called themselves “Pluto Underground“!
The community was there to build up the interest in a Pluto visit. And later on they were going to be the originators of leading ideas and plans of the candidate Pluto missions.
Previous Missions to Outer Planets – Waiting For Its Turn
Why did it take so long for our troublesome crew to break the undercover? What took that much time from 1989 till 2001 to actualize a Pluto mission?
While the primary reason was always the “budgetary limitations“, there is another major and clear reason: Human sent spacecrafts to all planets in Solar System for a closer view. And the latest visit to farthermost targets was to Neptune by Voyager 2 in 1989 after it passed Uranus in 1985. Besides that, although some of the previous missions including Voyagers had backup plans for a Pluto flyby, the options about visiting Pluto remained in the back seats for good.
Only remaining non-visited planet and the next known spot on the road was Pluto. In other words, “First things first“. Cliche, but makes sense!
Previous and Aborted Pluto Mission Plans
Although below will look like complete seperate studies of different mission plans, all can be considered to be built up on each other. Because the scientists playing roles on all were either the same people or they were in contact and the experiences were mutually shared on following projects. Pluto solidarity was not that massive as it is now, but it was a tough one!
First known project for a Pluto-focused reconnaissance flyby was named Pluto 350, a 350kg weight spacecraft. The study was developed by a team leaded by Robert Farquhar from Goddard Space Flight Center in 1989-1990. However it was never on the field.
Another plan for a direct Pluto visit was Pluto Fast Flyby Mission of NASA JPL in 1992 leaded by R. Staehle, which was later on called Pluto-Kuiper Express. The mission plan was very similar to New Horizons and was initially a lighter design (35-50kg) comparing to Pluto 350. However in the next steps of planning, the weight and the launching cost of the spacecraft became more and more.
Despite Alan Stern’s extreme efforts, that flyby mission plan was completely terminated in 2000 due to budgetary reasons. On the other hand, the studies for Pluto Fast Flyby Mission became drafts for New Horizons Mission and played an extremely important role in future Pluto exploration studies. Morever, it was year 2000 and New Horizons Mission was about to initialize!
Apart from direct visits, part of Mariner Mark II mission (1990) plan was including a visit to Pluto but that project shared a mutual destiny with above and was junked too.
Why Were Previous Pluto Missions Aborted?
On the published article “The New Horizons Pluto Kuiper Belt Mission: An Overview with Historical Context” in September 2007, Alan Stern; the leading person and Principal Investigator of New Horizons Mission states as follows:
“Of course, at the time this decision was made (he is mentioning Voyager Missions), Pluto’s atmosphere, small satellites, complex surface composition, and the entire Kuiper belt all remained undiscovered. By the time of the 1989 Voyager 2 flyby of Pluto-analog Triton, Pluto’s richness and context was beginning to be understood. This, combined with the fascinating results of Voyager 2’s Triton flyby that included a pathologically young surface, active geysers, and an atmosphere, motivated interest, particularly in a handful of young planetary scientists, to successfully appeal to NASA in 1989 to begin Pluto mission studies.“
So he believes the process in the beginning of 1990’s was a natural one.
Speaking of early 1990’s, it placed another major motive on the table for a Pluto visit: Discovery of Kuiper Belt.
In 1992, the first KBO (after Pluto and her moon Charon): Albion was discovered. And it was realized that Pluto, Charon and Albion had company: more than tens of thousands rocky celestial objects with a diameter more than 100km! That could easily change the game.
In short: The opportunities for a Pluto visit was on a roll with mid 1990’s. However when it comes to answer of the question on the header, the answer is: “It was still not the time yet”. Because more knowledge about those far worlds would increase the mobility of such mission which would make it more efficient. With that scientific aspect, the historical process continued to the new millenium.
New Horizons Mission Reasserts
While above motives and abortive missions laid the foundation of a Pluto and Kuiper Belt visit, the Underground Team was on duty: As the amount of knowledge about Kuiper Belt grew more and more, scientists were using it to build up the interest in Kuiper Belt and Pluto. In addition, they were trying to reduce the possibility of having another aborted mission because of “budgetary reasons“.
Did they face difficulties? Yes. Did they have to deal with politics? Yes. Did they stray from the intended way in more than a decade time? No!
Let’s skip the part where “politics” get involved and move on with the initialization of the mission:
Thanks to the scientists keeping the interest alive, NASA announced a new PKB (Pluto Kuiper Belt) AO (Announcement of Opportunity) on December 2000.
On 20 January 2001, New Horizons Mission was proposed to AO-OSS-01 (NASA’s Announcement of Opportunity of 2001) by a team of scientists as a PKB (Pluto-Kuiper Belt) flyby. The goal of the mission was to arrange a flyby close to Pluto-Charon System and ride on through the Kuiper Belt in extension, looking for more icy worlds to explore. In June 2001, the mission was selected for the next phase together with another one out of 5 and finally NASA confirmed the New Horizons Mission on 29 November 2001. The cost of the mission was calculated to be around $700 million from 2001 till 2016.
OK, finally a flyby mission to Pluto was in sight! But this should not prevent further questions, right?
Why Was New Horizons Mission Necessary and Feasible?
In other words, “Why Pluto, Charon and Other Kuiper Belt Worlds?”
Some part of the hint was given above: Pluto was the only planet which was not closely inspected. (Pluto was demoted to a dwarf planet after New Horizons Spacecraft was launched, but that’s another story..)
What’s more, Pluto and others mentioned above are the only type of objects we did not take a closer look in Solar System.
A superficial categorization of the major planetary objects in Solar System in terms of planetary structure and locations can be done as follows:
- Rocky Planets (Mercury, Venus, Mars).
- Gas Giants (Jupiter, Saturn, Uranus, Neptune)
- Big satellites of Gas Giants (Ganymede, Enceladus, Ariel, Triton etc)
- Kuiper Belt Objects (Planets like Pluto and Eris, together with other major rocky objects and their satellites like Charon)
Since human already performed successful close-by analysis from the list on 1-2-3, obviously it was time to step to number 4.
However, above are not the end of causes. Last but not least, the celestial objects stated on number 4 have some critical characteristics.
First of all, Pluto has an atmosphere while Charon doesn’t. Pluto was previously observed to have a unique, complex and possibly disappearing atmosphere because of dramatic temperature changes. Those temperature changes were considered to be a natural result of her distinctively eccentric orbit and axial tilt.
More exciting point was that Pluto surface was much more reflective than surface of Charon and existence of organic molecules and water ice were derived from atmospheric occultation and surface analysis data in 1990’s.
Pluto and Charon were also yielding the only known double planet system those times. But although they had a mutual destiny, their basic characteristics were so different from each other.
Besides the similarities and differences, although the area was extremely cold; those were considered to be “active” and “living” worlds.
One more surprising news popped up before New Horizons Spacecraft was launched: Hubble Space Telescope was focused on Pluto System for different scientific purposes and revealing more Pluto facts. In consequence, came up with the discovery of 2 new small moons (which were later named as Nix and Hydra)! This added an excitement boost to the mission, since Pluto became the only KBO with multiple satellites. As of today, we know there are a couple of more.
Actually we learnt another thing after New Horizons Spacecraft started its journey: Pluto had 2 more satellites which were later called Styx and Kerberos. We had to wait till 2011 and 2012 for the discoveries.
Scientific Significance of Kuiper Belt
Since rest of the bigger sized Kuiper Belt Objects supposed to have serious similarities with Pluto System, exploring additional targets in Kuiper Belt would most likely build up the information we have. That’s why it was thought to be a smart action to move on through Kuiper Belt after the Pluto flyby.
In addition to above, researchers working on formation of Solar System and Kuiper Belt understood that there are serious similarities and mutual consequences of both. And decoding the details about how Kuiper Belt objects were formed would lead to further understanding about Solar System structure as well as planetary formations.
What is more, those icy Kuiper Belt worlds had one thing in common: Water ice. Deeper analysis of the existence of water ice and its interaction with other icy materials (like methane and nitrogen) in Kuiper Belt was another important task.
The Window To New Worlds Was Half-Open
It was show time! Future was there to come. Human was going to have a closer look to Pluto, Charon and Kuiper Belt.
It took 12.5 years to make it feasible. And 13.5 years more was needed for preparing the project, constructing the spacecraft and arranging the flight. And some people dedicated their life to that. That’s beyond admirable!
On our next article, we explain the New Horizons Mission Goals.
Next articles in series include technical details about New Horizons Spacecraft. Thereafter you can check the articles 4 to 6 which tracks the mission timeline: New Horizons from Launching Till Pluto Encounter , Pluto Flyby. Another article for the Ultima Thule Flyby will be published soon.
- 09-2007, “The New Horizons Pluto Kuiper belt Mission: An Overview with Historical Context“
Link: ( https://arxiv.org/ftp/arxiv/papers/0709/0709.4417.pdf )
- 05-2018, “Alan Stern on the Pluto Revolution, the Psychology of Persistence, and “Chasing New Horizons””
Corey S. Powell
Link: ( http://blogs.discovermagazine.com/outthere/2018/05/04/alan-stern-on-chasing-new-horizons/#.XXoLPy4zbIU )
- 06-2015, “How’d We Get New Horizons? You Can Thank the Pluto Underground“
Link: ( http://www.astronomy.com/year-of-pluto/2015/06/howd-we-get-new-horizons-you-can-thank-the-pluto-underground )
12-2005, “New Horizons Press Kit“
Link: ( https://www.nasa.gov/pdf/139889main_PressKit12_05.pdf )
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