Happy 20th Anniversary, GPS!

From GPSWorld

The Global Positioning System marks its 20th year of operation on Monday, April 27.
Below is a timeline showing important milestones in the 20 years since the constellation reached full operational capability (FOC) on April 27, 1995.
FOC was formally announced on July 17, 1995. 

 ancient Satnav transit receiver

Before the GPS, the TRANSIT system, also known as NAVSAT (for Navy Navigation Satellite System), was the first satellite navigation system to be used operationally.
The system was primarily used by the U.S. Navy to provide accurate location information to its Polaris ballistic missile submarines, and it was also used as a navigation system by the Navy's surface ships, as well as for Hydrographic survey and geodetic surveying.
Transit provided continuous navigation satellite service from 1964, initially for Polaris submarines and later for civilian use as well.

Today, several satellite navigation systems with global coverage exist :

 Comparison of systems

source : wikipedia

Planet Earth gained five new navigation satellites in late March 2015, for four satellite systems.

Launched GNSS satellites 1978 to 2012

GPS. The U.S. Air Force’s ninth GPS Block IIF satellite (GPS IIF-9) launched on March 25 from Cape Canaveral, Fla.
The IIF-9 rode aboard a Delta IV rocket, the workhorse of the GPS fleet for successful launches.
The satellite was declared operational on April 21.
“Many thought the Delta IV and GPS days were long gone, but the recent questions concerning reliable and proven launch vehicles have brought them back online, so to speak,” said GPS World Defense Editor Don Jewell.
“The 20-year milestone for GPS space vehicles on orbit that occurred on April 27 translates to approximately 500 orbital years just for the IIR and IIF constellations alone. The IIAs may account for that many orbital hours as well.
“This is by far the most successful launch record ever put together by any nation or government. No other space-faring nation even comes close. The U.S. Air Force and all the players should be proud of all these records and more, plus we have one more GPS asset on orbit, providing GPS signals to the world and all they enable, courtesy of the USAF.”

Galileo. Two days later, March 27, a duo of Galileo satellites was successfully launched from Europe’s Spaceport in French Guiana.
The seventh and eighth Galileo satellites rode aboard a Soyuz ST-B rocket. Both are in their planned orbits.

IRNSS. The next day, March 28, the fourth satellite (IRNSS-1D) of  the IRNSS satellite navigation constellation was launched onboard PSLV-C27, and reached its orbital slot April 9.
The Polar Satellite Launch Vehicle blasted off from the Satish Dhawan Space Center on India’s east coast, in the 28th consecutive successful PSLV mission.

BeiDou. On March 30, China launched the first of a new generation of navigation satellites, BeiDou-3 M1, for its BeiDou constellation.
BeiDou-3 M1 is the first of 17 next-generation Beidou navigation satellites.
It will have a new navigation signal system with inter-satellite links and other tests to verify the satellite navigation system.
The new series of satellites is expected to mark an advancement in the completion of Beidou Phase III several years ahead of schedule, by as soon as 2017 rather than 2020.

GLONASS. Not making the March launch cut, GLONASS kept its hat in the orbit ring, so to speak, by issuing some far-sighted predictions.
Nicholas Testoyedov, CEO of Information Satellite Systems Reshetnev, said that the first GLONASS-K2 spacecraft will be launched into orbit in 2018.
“New code division (CDMA) signals will be emitted, so it will provide more accurate positioning for users.”
The GLONASS budget for 2015 will be cut by more than 5 billion rubles, a drop of more than 10 percent.
GLONASS is also suffering through an embezzlement scandal, related to construction of a new ground control center.

Quazi-Zenith Satellite System (QZSS). QZSS is a proposed three-satellite regional time transfer system and Satellite Based Augmentation System for the Global Positioning System, that would be receivable within Japan.

Links :

• Wired : Celebrating 25 years of not getting lost thanks to GPS
• GeoGarage blog : GPS status updated, higher accuracy expected / Europe's Galileo sat-nav spacecraft ready to fly / China GPS rival Beidou starts offering navigation data / Galileo: Europe's version of GPS reaches key phase / China switches on BeiDou Compass 'BDS' civilian nav-sat rival to GPS /

Getting lost

Gettinglost from iker elorrieta

This is somewhere in East Java where I had the opportunity to get lost for a few days with the great European surfers Tiago Pires and Aritz Aranburu during their break in the WCT Tour 2014.

Underwater macro footage

Lembeh Straits, A Macro Symphony from Kay Burn Lim

From MNN

In this exquisite "macro symphony," underwater photographer Kay Burn Lim gives viewers a glimpse of the awe-inspiring creatures that live under the waves of Indonesia's Lembeh Strait, a passage of water between Lembeh Island and the mainland city of Bitung.

The shallow strait is considered to be the premier muck diving capital of the world, and underwater photographers like Lim come from all over the world to document the wealth of creatures that lay hidden beneath these fragile sandy bottoms.

With the exception of the puffer fish (above) and the moray eel, all of the gorgeous marine critters you see in this video are no larger than two inches, and some of them are only as big as a grain of rice!

One of the most remarkable creatures featured in the video is the little leaf sheep nudibranch (Costasiella kuroshimae, pictured below), which is named for its obvious resemblance to, well, a sheep made of leafy greens!

Measuring only a few millimeters in length, these tiny photogenic sea slugs spend their days grazing on ocean algae — and perfecting their pokémon-like cuteness.

Macro Overture- Alor Archipelago, East Flores with the Komodo Dancer from Kay Burn Lim

Europe's Goce gravity satellite probes Earth's mantle

 Goce detects deep plumes of mantle material rising from more than 2,000km down

From BBC by Jonathan Amos

Europe's Goce gravity satellite has provided striking new visualisations of the Earth's deep interior.
Its gravity data has enabled the effect of variations in the density of rock to be traced up to more than 2,000km below the surface.
The maps, published by the journal Nature Geoscience, help to show how material moves up and down, driving a range of geological phenomena.
These include subduction zones, where the great tectonic slabs covering the Earth's surface dive under one another.
"Ultimately, volcanic activity and earthquakes occur because of these slow movements inside the Earth's mantle," explained Dr Isabelle Panet from the Institute for Geographic Information and Forestry, Paris, France.
"The volcanoes and earthquakes are, if you like, just the surface expression of these deep dynamics," she told BBC News.

By tracking the speed at which waves of energy from tremors propagate through rock, scientists can determine the structure of the Earth's interior - a technique known as seismic tomography.
But to convert these speed variations into densities, seismic tomography leans on quite a few assumptions, including the temperature and composition of the rock at various depths.
Determining these density differences is, however, essential to derive the relative buoyancy of material.
This might be hotter, lighter material on its way up, such as in a plume of magma; or cold dense rock on its way down, such as a swathe of oceanic crust descending at one of those subduction zones.

Goce offers some complementary information.
The satellite, which flew from March 2009 until November last year, gathered unprecedented information on the subtle changes in the pull of gravity around the Earth.
These deviations reflect differences in the mass, and by extension the density, of material at depth.
By viewing the rate of change, or gradient, in the acceleration due to gravity in three separate directions, Dr Panet and colleagues have been able to pull out a number of interesting features from the data.

 The satellite finds traces (circled red regions) of ancient subduction zones

running deep under Asia and along the Americas

These include major mantle plumes in the Pacific and south-east of Africa.
Also visible are ancient subduction zones running deep under Asia and along the Americas.
What Goce is probably seeing is the buried remnants of old plate material of Jurassic age (older than 150 million years ago) in the case of Asia, and of roughly Cretaceous age (older than about 60 million years ago) in the case of the Americas.

In addition, the satellite's gravity data contains a residual signal of the former Tethys Ocean. Subducted material is seen in the maps stretching from the Mediterranean to the Himalayas.
The Tethys Ocean is thought to have closed in the past 40-50 million years as India and Asia collided.
Dr Panet said: "The main interest of these gravity gradient data is to use them in combination with seismic tomography because the maps of seismic velocity anomalies - they do not give you the mass.
"And the mass is a very important parameter to understand the dynamics of the mantle because it creates the buoyancy forces that drive material up and down. Now, by combining the structural information from seismic tomography and the mass sensitivity of the Goce data, we can better understand the dynamics of the mantle's convective fluids."

Goce's ability to sense the uneven distribution of mass through the Earth has already allowed scientists to map the boundary globally between the Earth's crust and the mantle - the so-called Moho boundary.
The famous "discontinuity" lies some 10-70km below the surface and marks a sharp change in rock properties.
Other researchers are investigating old plate movements by linking gravity signals on different continents, such as on Africa and South America, to show how they were once joined together.
"What we are seeing is that Goce data enable us to sense features from really quite shallow regions in the crust, down to very deep in the mantle," commented Dr Rune Floberghagen, the European Space Agency's mission manager for Goce.

 The circled blue region reflects remnants of the old Tethys Ocean

 Note : The Eotvos is a unit for the rate of variation of the gravitational acceleration.

Links :

• GeoGarage blog :  Goce gravity map traces ocean circulation / Goce gravity mission traces ocean circulation / Gravity satellite yields 'Potato Earth' view / Earth's gravitational field mapped by researchers
• ESA : Goce help tap into sustainable energy resources

Oceans are world's seventh largest economy worth $24tn, says WWF report

‘The oceans are in a bad state that is rapidly getting worse.

Fisheries are starting to collapse, there are record levels of pollution, such as plastic pollution, and there is climate change.’

Photograph: David Fleetham/naturepl.com/WWF

From The Guardian by Oliver Milman

Vast economic worth of world’s oceans includes fishing, tourism and shipping but is declining due to pollution, climate change and overfishing

The monetary value of the world’s oceans has been estimated at US$24tn in a new report that warns that overfishing, pollution and climate change are putting an unprecedented strain upon marine ecosystems.
The report, commissioned by WWF, states the asset value of oceans is $24tn and values the annual “goods and services” it provides, such as food, at $2.5tn.
This economic clout would make the oceans the seventh largest economy in the world although the report’s authors, which include the Boston Consulting Group, say this is an underestimate as it does not factor in things such as oil, wind power and intangibles, such as the ocean’s role in climate regulation.
The economic value is largely comprised of fisheries, tourism, shipping lanes and the coastal protection provided by corals and mangroves.

photo : Mark A Johnson

However, the oceans are facing mounting pressures.
They soak up around half of the carbon dioxide pumped into the atmosphere by human activity, a process that is warming the water and increasing the acidification of the ocean.
The report warns that nearly two-thirds of the world’s fisheries are “fully exploited” with most of the rest overexploited.
The biological diversity of the oceans slumped by 39% between 1970 and 2010, while half of the world’s corals and nearly a third of its seagrasses have disappeared in this time.

Professor Ove Hoegh-Guldberg, lead author of the report and director of the Australia-based Global Change Institute, said it was important that the business community understood the value of the oceans so that a strategy could be devised to reverse its decline.
“If you don’t look after an asset like the ocean it starts to degrade so it’s important we start to solve these problems now on an international basis,” he said.
“The oceans are in a bad state that is rapidly getting worse. Fisheries are starting to collapse, there are record levels of pollution, such as plastic pollution, and there is climate change.”
Hoegh-Guldberg said the “shocking” rate of change in the world’s oceans was illustrated in the latest report by the UN’s climate science panel, which stated that changes in the ocean’s chemistry due to an increase in CO2 emissions was faster than at any point in the past 65m years.
Warming temperatures can make life challenging for some marine species, while the acidification of the ocean hampers the ability of creatures such as corals and molluscs to form their shells and skeletons.

“The changes we are making will take 10,000 years at least to turnaround, so we don’t want to go down this pathway,” Hoegh-Guldberg said.
“This generation of humans is defining the future of 300 generations of humans. We are conducting these experiments with our world despite the consequences for people.”
Hoegh-Guldberg said that nations should do more to manage localised issues such as pollution and overfishing to help oceans deal with climate change.
“If you protect marine areas and regulate fishing, you can help corals survive the impact of climate change,” he said.
“If we solve these local problems we can buy some time while we deal with the global climate issue. But let’s not pretend here – if we don’t get off the current CO2-rich pathway we’re on now, all the attempts to control local factors won’t work. Coral reefs will become a distant memory and the ability to feed people will be severely degraded.”
The report calls for eight key steps to revive the health of the oceans, including a stronger focus in UN agreements on oceans, deep cuts to emissions, at least 30% of marine areas to be protected by 2030 and greater action to tackle illegal fishing.

Links :

• Nature : Oceans are 'worth US$24 trillion'
• WWF Ocean Panda