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Ocean Surface Topography from Space
Riding the Waves with Jason-1 - A Q&A with Two Mission Leaders
December 01, 2006

Successful space missions require much more than just great technology, they need dedicated people to create them, operate them and make the most of the information they provide. Leading the engineers, technicians and scientists behind Jason-1 are Project Manager Mark Fujishin and Project Scientist Dr. Lee-Lueng Fu. Here's a brief look at the mission from their unique perspectives.

Project Manager Mark Fujishin

Jason-1 Project Manager - MarkFujishin
Project Manager Mark Fujishin
Image credit: NASA/JPL
How long have you been involved with the TOPEX/Poseidon and Jason-1 missions and in what roles?

I joined the TOPEX/Poseidon mission as a systems engineer for the spacecraft contractor, the Fairchild Space Company, in late 1987 and eventually became the project manager. Similar to many members of the TOPEX/Poseidon team who concurrently supported Jason-1, I also acted as the Jason-1 mission manager prior to my current assignment as project manager.

As project manager, what have been the major administrative and engineering challenges with Jason-1 mission?

Since Jason-1 is a joint international partnership between NASA and the French Space Agency (CNES), communication and understanding between the two agencies requires constant attention. Although we clearly share common overall goals, sometimes the methods and paths to achieve them will vary somewhat.

Technically, our greatest concern at this juncture is one common to other successful missions - how to keep the team motivated and involved over the long term as the operations become more routine. We have been able to overcome this primarily by cultivating a multi-mission support group, which works several missions in parallel to keep the work interesting and challenging.

What's been the most rewarding aspect of the Jason-1 mission so far?

In reaching this five-year operational milestone, Jason-1 has clearly established itself as another tremendous accomplishment in the continuing NASA/CNES partnership. The real satisfaction here is knowing that the Jason-1 team had big shoes to fill from the legacy of TOPEX/Poseidon and can now revel in that outstanding achievement. Conversely, those associated with TOPEX/Poseidon can also see how their work directly led to the success of Jason-1.

Are there new technologies being developed for future altimetry missions?

Of course, success often begets success; even more accurate and efficient altimetry instruments have already been developed for inclusion on missions such as the Ocean Surface Topography Mission/Jason-2. However, the biggesthurdle is probably in reducing the cost and development timefor these missions due to continuous demands on the overall NASA budget.

Project Scientist Dr. Lee-Lueng Fu

Project Scientist Dr. Lee-Lueng Fu
Project Scientist Dr. Lee-Lueng Fu
Image credit: NASA/JPL
How long have you been involved with the TOPEX/Poseidon and Jason-1 missions and in what role?

I started working on TOPEX/Poseidon in 1986 and became the project scientist in 1988. I wrote the mission's science plan together with Robert Stewart, who was the project scientist from 1980-87. I was also a principal investigator leading a research team to study ocean circulation using the mission's data and numerical models.

Before launch, I was heavily involved in mission planNiñg, making sure that the design met science requirements. This involved difficult trade-offs, such as mission resources versus science benefits. A critical consideration was a concern about potentially faulty batteries versus a lengthy launch delay. I organized the science team to assess the science impact of a potentially shortened mission. Fortunately the mission surprised everyone and produced a 13-year-long data record surpassing anyone's wildest expectations before launch.

After launch, I led the science team to evaluate the quality of the data. After realizing the revolutionary performance of the mission, I began advocating for a follow-on mission to TOPEX/Poseidon in 1993, eventually leading to the formation of Jason-1. In the mean time, I was engaged in science work using the remarkable data from the mission, participating in the detection of the biggest El Niño of the 20th century, as well as using numerical models to assimilate the data for optimal estimation of the ocean circulation, which resulted in the collaborative ECCO (Estimation of the Circulation and Climate of the Ocean) project with the Massachusetts Institute of Technology and Scripps Institution of Oceanography.

As project scientist, what have been your biggest challenges with Jason-1 mission?

As the follow-on to TOPEX/Poseidon, the challenge of Jason-1 is to repeat the remarkable performance of its predecessor.

Before launch, the science team requested that Jason-1 be flown in tandem with TOPEX/Poseidon along the same track but separated in time by less than 10 minutes. In this configuration, the two satellites essentially measure the same spot of the ocean in nearly identical conditions. This allowed us to cross-calibrate the measurements from the two satellites and make a seamless transition from TOPEX/Poseidon to Jason-1 in order to build a long and consistent data record for studying long-term ocean change. This unprecedented experiment was successfully carried out, leading to a continuing data record of the global ocean sea level and circulation since 1992.

The science team also made a challenging request to start a formation flight of TOPEX/Poseidon and Jason-1 in an interleaving orbit after the cross-calibration period was completed. The science tandem mission began in September 2002, doubling the coverage of the ocean and leading to enhanced resolution to study ocean currents, eddies, coastal circulation and tides.

What is your own specific area of research and what have you found most scientifically interesting from the Jason-1 mission?

My personal interests are to study the dynamics of ocean circulation. The unprecedented accuracy of TOPEX/Poseidon and Jason-1 created the first opportunity to study the large-scale, rapidly changing sea level patterns that were not observable to in situ measurements.

I discovered such patterns in remote ocean basins in the Southern Ocean, the central North Pacific Ocean, as well as the Argentine Basin of the South Atlantic Ocean. I was able to explain the dynamics of such patterns using the wind observations from satellite scatterometers. The only exception was the Argentine Basin, where the ocean has a natural oscillation in response to a wide range of excitations, including small-scale ocean eddies, or storms of ocean currents. By combiNiñg Jason-1 data with other altimeter data from the European ERS and Envisat missions, I was able to show that ocean eddies are exchanging energy with larger-scale waves, a dynamic phenomenon not known before.

The promise of the wonderful data record from TOPEX/Poseidon and Jason-1 is not yet fully realized, and I am continuously surprised by new findings with great pleasure.

What are some of the questions about the ocean that Jason-1 and future altimetry missions may help answer?

As the length of the data record grows, we are discovering oceanic phenomena on ever increasing time scales. For the first time in history, large-scale changes in the ocean on decadal time scales have been mapped over the entire global oceans. Scientists are busy unravelling the mysteries causing these changes and their possible link to long-term climate variability. The continuation of Jason-1 and its follow-on, the Ocean Surface Topography Mission /Jason-2, will play a crucial role in establishing a permanent observing system for studying these long-term changes in the ocean, which stores over 80 percent of the heat from global warming and holds the key to understanding the rate of future warming and its consequences to society.

Despite the success of TOPEX/Poseidon, Jason-1 and the future Jason-2, a single altimeter system cannot fully measure the energetic variability of the ocean at scales smaller than about 300 kilometers. This so-called mesoscale variability is responsible for 90 percent of the kinetic energy of the ocean and is key to understanding the dynamics of the ocean and its interaction with the atmosphere and biosphere, among with many other important practical applications such as ship routing, fisheries, offshore drilling and hurricane forecasting.

Mapping this mesoscale variability in the ocean from space presents the next challenge. This challenge can be met with radar interferometry, technology whose development was started by NASA's Instrument Incubator Program eight years ago. The task ahead is to fly this instrument in space to make the next revolution in oceanography.

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