physics

Jason-1

Jason-1 is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Jason-1 rather than just read about it. In short: Jason-1 was a satellite altimeter oceanography mission. It sought to monitor global ocean circulation, study the ties between the ocean and the atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño and ocean eddies.

Key takeaways

Jason-1 belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Jason-1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Jason-1 from memory before moving on to harder problems.

Reference excerpt

Jason-1 was a satellite altimeter oceanography mission. It sought to monitor global ocean circulation, study the ties between the ocean and the atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño and ocean eddies. Jason-1 was launched in 2001 and it was followed by OSTM/Jason-2 in 2008, and Jason-3 in 2016 – the Jason satellite series. Jason-1 was launched alongside the TIMED spacecraft.

Naming The lineage of the name begins with the JASO1 meeting (JASO=Journées Altimétriques Satellitaires pour l'Océanographie) in Toulouse, France to study the problems of assimilating altimeter data in models. Jason as an acronym also stands for "Joint Altimetry Satellite Oceanography Network". Additionally, it is used to reference the mythical quest for knowledge of Jason and the Argonauts.[1] Archived 25 March 2016 at the Wayback Machine[2][3] This article incorporates text from this source, which is in the public domain.

History Jason-1 is the successor to the TOPEX/Poseidon mission, which measured ocean surface topography from 1992 through 2005. Like its predecessor, Jason-1 is a joint project between the NASA (United States) and CNES (France) space agencies. Jason-1's successor, the Ocean Surface Topography Mission on the Jason-2 satellite, was launched in June 2008. These satellites provide a unique global view of the oceans that is impossible to acquire using traditional ship-based sampling. Jason-1 was built by Thales Alenia Space using a Proteus platform, under a contract from CNES, as well as the main Jason-1 instrument, the Poseidon-2 altimeter (successor to the Poseidon altimeter on-board TOPEX/Poseidon). Jason-1 was designed to measure climate change through very precise millimeter-per-year measurements of global sea level changes. As did TOPEX/Poseidon, Jason-1 uses an altimeter to measure the hills and valleys of the ocean's surface. These measurements of sea surface topography allow scientists to calculate the speed and direction of ocean currents and monitor global ocean circulation. The global ocean is Earth's primary storehouse of solar energy. Jason-1's measurements of sea surface height reveal where this heat is stored, how it moves around Earth by ocean currents, and how these processes affect weather and climate.

Jason-1 was launched on 7 December 2001 from Vandenberg Air Force Base, in California, aboard a Delta II Launch vehicle. During the first months Jason-1 shared an almost identical orbit to TOPEX/Poseidon, which allowed for cross calibration. At the end of this period, the older satellite was moved to a new orbit midway between each Jason ground track. Jason had a repeat cycle of 10 days. On 16 March 2002, Jason-1 experienced a sudden attitude upset, accompanied by temporary fluctuations in the onboard electrical systems. Soon after this incident, two new small pieces of space debris were observed in orbits slightly lower than Jason-1's, and spectroscopic analysis eventually proved them to have originated from Jason-1. In 2011, it was determined that the pieces of debris had most likely been ejected from Jason-1 by an unidentified, small "high-speed particle" hitting one of the spacecraft's solar panels. Orbit maneuvers in 2009 put the Jason-1 satellite on the opposite side of Earth from the OSTM/Jason-2 satellite, which is operated by the United States and French weather agencies. At that time, Jason-1 flew over the same region of the ocean that OSTM/Jason-2 flew over five days earlier. Its ground tracks fell midway between those of OSTM/Jason-2, which are about 315 km (196 mi) apart at the equator. This interleaved tandem mission provided twice the number of measurements of the ocean's surface, bringing smaller features such as ocean eddies into view. The tandem mission also helped pave the way for a future ocean altimeter mission that would collect much more detailed data with its single instrument than the two Jason satellites now do together. In early 2012, having helped cross-calibrate the OSTM/Jason-2 replacement mission, Jason-1 was maneuvered into its graveyard orbit and all remaining fuel was vented. The mission was still able to return science data, measuring Earth's gravity field over the ocean. On 21 June 2013, contact with Jason-1 was lost; multiple attempts to re-establish communication failed. It was determined that the last remaining transmitter on board the spacecraft had failed. Operators sent commands to the satellite to turn off remaining functioning components on 1 July 2013, rendering it decommissioned. It is estimated that the spacecraft will remain on orbit for at least 1,000 years. The program is named after the Greek mythological hero Jason.

Satellite instruments

Jason-1 has 5 instruments:

Poseidon 2 – Nadir pointing Radar altimeter using C band and Ku band for measuring height above sea surface. Jason Microwave Radiometer (JMR) – measures water vapor along altimeter path to correct for pulse delay DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) for orbit determination to within 10 cm or less and ionospheric correction data for Poseidon 2. BlackJack Global Positioning System receiver provides precise orbit ephemeris data Laser retroreflector array works with ground stations to track the satellite and calibrate and verify altimeter measurements. The Jason-1 satellite, its altimeter instrument and a position-tracking antenna were built in France. The radiometer, Global Positioning System receiver and laser retroreflector array were built in the United States.

Use of information TOPEX/Poseidon and Jason-1 have led to major advances in the science of physical oceanography and in climate studies. Their 15-year data record of ocean surface topography has provided the first opportunity to observe and understand the global change of ocean circulation and sea level. The results have improved the understanding of the role of the ocean in climate change and improved weather and climate predictions. Data from these missions are used to improve ocean models, forecast hurricane intensity, and identify and track large ocean/atmosphere phenomena such as El Niño and La Niña. The data are also used every day in applications as diverse as routing ships, improving the safety and efficiency of offshore industry operations, managing fisheries, and tracking marine mammals. TOPEX/Poseidon and Jason-1 have made major contributions to the understanding of:

Ocean variability

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Jason-1

Start with the simplest possible case. Write down what Jason-1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Jason-1 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Jason-1 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Jason-1

In research: Jason-1 appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Jason-1 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Jason-1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2001 in France, CNES satellites, Earth observation satellites of France, so understanding it makes those chapters shorter.
In everyday life: Look for Jason-1 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Jason-1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Jason-1 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Jason-1 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Jason-1 in simple terms?

Why does Jason-1 matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Jason-1?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Jason-1.