. Why  Spacecrafts' Missions are Extended?

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VOYAGER 1& 2

 
 

 
 

Voyager 1 & 2

At this moment, Voyager 1 and 2 are traveling away from the Sun, probing the outer edges of our solar system and analyzing the interaction of the solar wind and the interstellar medium nearly four decades after launch. The two Voyager spacecrafts have contributed to our understanding of the giant planets of our solar system as well as the limits of the Sun’s influence, but it is easy to forget that both Voyagers ended their primary mission phases soon after their encounters with Saturn, which for Voyager 2 occurred in summer 1981. More than 30 additional years of scientific discovery by the Voyagers have resulted from repeated extensions of the mission. LEARN MORE about THIS FANTASTIC VOYAGE

Benefits of Some Mission Extensions

During 2016, almost 10 active missions were in the Astrophysics Division. Follow some examples of Science Results Made Possible by Extended Missions in Astrophysics.

Chandra X-Ray Observatory 

Discovery of the most recent known supernova explosion in our galaxy with an age of around 140 years, about 200 years younger than previous record-holder (Reynolds et al., 2008).

Kepler

Great enhancement of the population of small, rocky planets orbiting Sun-like stars and stars with astro-seismology periods.

During 2016, there were approximately 20 active missions in this division. Follow some examples of Science Results Made Possible by Extended Missions in Earth Science.

CALIPSO

CALIPSO observations showed gradually increasing stratospheric aerosol loading from 2006-2011 due to a series of relatively moderate volcanic eruptions (Vernier et al., 2011) and resulting in a global cooling of about −0.07°C (Solomon et al., 2011), sufficient to offset a significant portion of the surface warming expected from
increasing greenhouse gas concentrations over the past decade.

Jason-1/Jason-2(OSTM)

The Jason-1/Jason-2 (OSTM) observation record now stretches over 20 years, providing the most accurate and complete understanding of sea level change. The extended mission phases of Jason-1 and Jason-2 improved estimates of deep ocean topography, resolving many presently unknown seamounts and geologic features on the ocean bottom.

The Heliophysics Division during 2016 was responsible for approximately 16 active missions. Follow some examples of Science Results Made Possible by Extended Missions in Heliophysics.

STEREO

In its extended mission, STEREO obtained the first 360 degree images of the Sun.

THEMIS/ARTEMIS

Conversion of magnetic energy in the magnetotail to particle energy in the inner magnetosphere was observed (Angelopoulos et al., 2013), particularly in conjunction
with the Van Allen Probes (THEMIS). Retargeting two of the  five spacecraft to circumlunar orbits (ARTEMIS) allowed for the first fully quantitative analysis of the structure and dynamical processes characteristic of the lunar wake (Wiehle et al., 2011).

SOURCE: *Extending Science: NASA's Space Science Mission Extensions and the Senior Review Process / ISBN 978-0-309-44878-9 | DOI: 10.17226/23624 / AUTHORS: Committee on NASA Science Mission Extensions; Space Studies Board; Division on Engineering and Physical Sciences; National Academies of Sciences, Engineering, and Medicine - Copyright 2016 by theNational Academy of Sciences. All rights reserved.

Why Spacecrafts' Missions are extended? 

Today, nearly four decades after their launch in 1977, spacecraft Voyager 1 and 2 are traveling away from the Sun, probing the outer edges of our solar system and analyzing the interaction of the solar wind and the interstellar medium.

By their odyssey, they do an incredible contribution to our understanding of the giant planets of our solar system as well as the limits of the Sun’s influence.

As we know, both Voyagers ended their primary mission phases soon after their encounters with Saturn which, for Voyager 2, occurred in summer 1981. The 30 additional years missions allowed to Voyagers 1 and 2, given us a lot of scientific discoveries.

Who make the decision for additional years?

When a spacecraft is first time launched, it is in the Prime Phase of its mission, which can be one to several years. In this phase, it focus on achieving a specific set of mission objectives aimed at answering high-priority science questions.

NASA’s Science Mission Directorate (SMD) operates approximately 60 of these spacecrafts, with more than 20 under development. As well as some missions have multiple of them, they are all sponsored by the Astrophysics, Heliophysics, Earth Science, and Planetary Science Divisions.

Spacecrafts last through their proposed Prime Mission because they are tested in harsh conditions similar to those found in the space vacuum of their target mission. 

An extended mission is possible when we can receive more valuable scientific data and the spacecrafts are fit to pursue their travel in space. For that latter case, engineers designed them to do so.

But, extended a mission is expensive. SMD allocate slightly less than one-third ($5.6 billion) of NASA’s overall budget of $19.3 billion in 2016. 

What is an Extended Mission?

All NASA missions progress through phases A to F, as early concept studies (A), operational or prime phase (E) and end of life (F).

Typically, many spacecrafts continue working after completing their prime phase because they are in good shape to do more. But, when a mission nears the end of its prime phase, the project' team (as the Planetary Science Division) can request a mission extension through the relevant division’s Senior Review process.

Extended operation may be approved if a mission can collect data that will help to answer new science questions that were not anticipated when the mission was first time formulated, or extend the existing data sets and improve understanding of the subjects being investigated.

Examples of successful Extended Mission accepted

The Planetary Science Division use flexibility in its regime of mission review for occasional mission-specific adjustments to review timing. That is necessary due to the special constraints of such planetary missions who target body encounters or critical mission events that require the undivided attention of the team members because they have to write the Senior Review proposal!

Also, the 3-year extension accepted for Cassini in the 2014 Senior Review because the mission’s “Grand Finale” scenario in 2017 would require more than the nominal 2-year extension period. So, the mission would be terminated due to the lack of fuel and the need to dispose Cassini for reasons of planetary protection. The Senior Review received no request for 2016. That is what we say “an natural dead” and it’s correct.

Like we had see, the Planetary Science Senior Review panels are sometimes split into separate sub-panels by subject matter.

The average budget for SMD over the 5-year period of 2011 to 2015 was $5.03 billion and, the extended missions accounted for 11.3 percent of that.

How we decide which one mission to Extend?

A key aspect of the process for extending NASA science missions is the Senior Review. The requirement for this review is established in the legislation as follows: The Administrator shall carry out biennial reviews within each of the science divisions to assess the cost and benefits of extending the date of the termination of data collection for those missions that have exceeded their planned mission lifetime.

The requirement was initially established in the 2005 NASA Authorization Act and repeated in the 2010 NASA Authorization Act. NASA ASD began conducting Senior Reviews of its missions in the early 1990s and established a 2-year cadence for such reviews.

The 2013 SMD Handbook states that after a mission’s prime phase, entry into an extended phase “is possible if part of a compelling investigation contributes to NASA’s goals” (NASA, 2013). This document defines also SMD’s implementation for the Senior Review process, which is codified, yet flexible for the needs of each division, and involves an evaluation of the productivity of the proposed extended mission by members of the scientific community.

But, in NASA' history, we have some exceptions!

The erupting jets and curtains of water on Enceladus.

SOURCE: NASA Jet Propulsion Laboratory, “Encroaching
Shadow,” accessed June 27, 2016,
http://www.jpl.nasa.gov/spaceimages/
details.php?id=PIA17184; courtesy of NASA/ JPLCaltech/Space
Science Institute.

Mission' Teams improvement

For the mission teams, the preparation of Senior Review proposals and presentations requires a tremendous amount of work.

Related by many mission team members who met the committee, at every 2-year period, it is typically requires up to 6 months to prepare for and present at a Senior Review. Challenge come with the fact that, all the job diverts mission teams of producing scientific results with their spacecraft during this period.

Also, representatives from mission teams reported that they have a lot of questions from the panel with very limited time to prepare responses!

For the Committee of National Academy Press, it is clear, NASA science divisions should be allowed to conduct reviews out of phase to allow for special circumstances and should have to add flexibility in organizing their reviews to take advantage of unique attributes of each division’s approach for science.

Also, each division should ensure that their timelines allocate sufficient time for each stage of the Senior Review process, including a minimum of 6 to 8 weeks from
distribution of proposals to the panels until the panel meets with the mission teams. The panels should have at least 4 weeks to review the proposals and to formulate
questions for the mission teams, and the mission teams should be allocated at least 2 weeks to generate their responses to the panel questions.

MISSIONS 2016 Senior Review of Operating Missions

The NASA Science Mission Directorate (SMD) conducts independent, comparative reviews of operating missions within each division to maximize the scientific return from these missions within finite resources. NASA uses the findings from the Senior Review to define an implementation strategy and give programmatic directions to the mission and projects concerned.

The 2016 Planetary Mission Senior Review (PMSR-16) was conducted from May16-26th for 9 missions: Curiosity, Dawn, Lunar Reconnaissance Orbiter (LRO), Mars Express (MEx), Mars Reconnaissance Orbiter (MRO), New Horizons, Odyssey, Opportunity, and Mars Atmosphere and Volatile EvolutioN (MAVEN).

Benefits of Some Mission Extensions

During 2016, there were approximately 14 active Planetary Science Division missions. Follow some examples of Major Science Results Made Possible by Extended Missions in Planetary Sciences.

Cassini

Global subsurface oceans were discovered in Titan (Lorenz et al., 2008; Iess et al., 2012) and in Enceladus (Thomas et al., 2016).

MERs Spirit and Opportunity

A habitable hydrothermal environment was discovered by the Spirit rover (Squyres et al., 2008; Ruff et al., 2011). The Opportunity rover, along with MRO, mapped hydrated
magnesium and calcium sulfate minerals that formed from rising ground waters(Arvidson et al., 2015).

Mars Odyssey

Extensive chloride-bearing deposits were discovered, likely ancient playas (Osterloo et al., 2008).

Mars Reconnaissance Orbiter (MRO)

Recurring slope lineae were discovered (McEwen et al., 2011) and their association with hydrated salts was studied (Ojha et al., 2015).

Mars Science Laboratory

The Curiosity rover arrived at the base of Mt. Sharp and discovered evidence for a long-lived lake (Grotzinger et al., 2015). Evidence of refractory organic material on Mars was discovered (Eigenbrode et al., 2015).

NEOWISE

Earth’s Trojan asteroid was discovered (Connors et al., 2014).

Voyager 2 (& 1)

The first exploration of ice giant systems was completed of Uranus (Stone, 1987) and Neptune and Triton (Stone and Miner, 1989).

On the left, the Mars Reconnaissance Orbiter not only performs extended mission science at Mars but also serves as a relay spacecraft for the Opportunity and Curiosity rover missions. Ending operating Mars orbiters would eliminate vital infrastructure supporting other missions in both prime and extended phase.

SOURCE: NASA, Image PIA04916, December 10, 2003; courtesy of NASA/JPL-Caltech.