ROSETTA-Ice launches five more ALAMOS

ROSETTA-Ice launched five more ALAMO ocean profilers from an Air National Guard C-130 Hercules yesterday. First clear day for weeks, and the last available day to fly. Graphic shows the deployment locations.

These profilers should report back daily while sea ice is clear. In winter, they will be covered by sea ice but will continue to profile, then send us back their data next summer when the ice clears away again.

Congratulations to the entire ROSETTA-Ice team, but in particular Kirsty Tinto and Dave Porter (Lamont-Doherty Earth Observatory) and Scott Springer (ESR).
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Read more at ESR’s Facebook page.

ROSETTA-Ice launches first Alamo float in Ross Sea

Scott Springer (ESR) was part of the team making the first successful launch of an Alamo (air-launched autonomous micro observer) profiling float in the Ross Sea. The Alamo float measures profiles of temperature and salinity from the surface to the seabed in this difficult-to-reach part of the world. About once per day, the profiler comes to the surface and makes a phone call to send its data home to researchers in the US.

Learn more here.

ALAMO, take 2

We return to the ocean the next day with better weather

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A clear view of open water at our proposed drop site.

The crew flies over our proposed site, descends to 300 feet and then climbs back to 2500 feet to check the wind speed and direction. While we turn around to return to the drop site, the cargo deck crew prepares the ALAMO float.

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The crew prepares to open the cargo door as we near the drop site.

We scientists are seated along the sides (with our seatbelts fastened) and the loadmasters don harnesses and tether themselves to anchor points on the cargo deck.  It’s time to open the cargo door!

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With the cargo door open, the backlighting overwhelms my camera. Sgt. Ray is prepared to give the signal to launch.  The line going upward will trigger the parachute deployment when the float falls away from the plane.

When the navigator tells the loadmaster that we are at the proper location, they launch the ALAMO, its parachute deploys, and it drifts out of sight quickly, before we can see if it landed in the water.

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Sgt Ray watches the orange parachute of the ALAMO float drift away (Photo: Tej Dhakal)

Everyone wants to know that the ALAMO landed safely in the water, so Major Hicks circles back several times while we search the surface of the ocean for the orange parachute.  We never saw any sign of it.

When we land, Kirsty comes on board with a smile on her face and says that the ALAMO float has already sent us an email to say that it has successfully made its first measurements!

ALAMO floats

In addition to mapping the properties of the Ross Ice Shelf with the IcePod, we measuring the ocean properties just north of the ice shelf. We will do this with ALAMO floats (Air Launched Autonomous MicroOberserver). ALAMO floats measure three critical properties of the ocean: temperature, salinity, and pressure. They do this while slowly sinking to the bottom of the ocean and then rising back to the surface. When they are at the surface, they place a phone call via Iridium satellites and literally email their data back to us.

ALAMO floats are a fairly new technology which has been used mostly in warm subtropical waters to date. A major complication in polar waters is the possible presence of sea ice. The ALAMO floats have a sea-ice-avoidance algorithm that detects whether there is likely to be sea ice as they rise upward, and to not surface if sea ice is likely to be present. The sensors and communications electronics are on top of the float, and we don’t want it to get damaged by running into sea ice from below.

The floats are deployed from the air, which makes it possible to go places that ships can’t go. A perfect example of such a location is the waters just north of the Ross Ice Shelf. In this region, the sea ice melts out near the ice shelf in late November while there is still lots of ice to the north, keeping ships away. An icebreaker, the Nathaniel B. Palmer, is the first ship scheduled to visit this region in late January. By deploying the ALAMO floats by airplane, we can make ocean measurements 6-8 weeks sooner than we could make them from a ship. These springtime measurements will contribute to our understand of the seasonal cycle of the sea ice in this region.

Our first challenge is that we need to be able to see where we are deploying the floats. In particular, we need a day without low clouds, which are quite common in this area. Our second challenge is that we need to be sure that we are dropping the floats into water and not onto sea ice. Satellite images help us in our planning, but in the end we just have to fly out there and look firsthand.

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A forklift delivers the ALAMO float to the cargo hold of the C130. The float is inside a cardboard box so that the parachute cords do not snag the sensors during the launch. When it hits the water, the box falls apart and the ALAMO floats away.
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The crew members run through their procedures for the launch before we take off. This is just the last of many discussions. They are very careful about throwing things out of airplanes!
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When we get out over the ocean, we find lots of sea ice and low clouds. The pilot decides that visibility is too poor to try the launch, so we return to the ice shelf to do some IcePod mapping instead. ALAMO will have to wait for another day.

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Looking out the window

start

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The flight crew invites Isabelle and me to sit on the flight deck for take off.
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We fly by the summit of Mt Discovery shortly after leaving Willie Field. Minna Bluff extends about 30 miles to the east (upward in this picture).
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We fly southward along the Transantarctic Mountains, which provide dramatic scenery.
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Large glaciers flowing out of the mountains are the source of ice that becomes the Ross Ice Shelf along its western side.

We turn eastward and fly away from the mountains.  The ice shelf is a  sheet of snow-covered ice as far as the eye can see. In places where ice is under stress, it forms large cracks known as crevasses.

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Crevasse field

but for the most part the ice shelf is nearly featureless except for small wind ripples in the snow.

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Shadow of plane on the snow.

Although the vast, often featureless ice shelf is an amazing sight, there is much more to be learned from our instruments than from looking out the window.

Shakedown flight

 

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Part of the ROSETTA crew walking out to the plane at Williams Field.
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Kirsty is the Field Principal Investigator whose job is to keep the thirteen of us working like a machine. Here she gives some last minute instructions before the flight.
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Tej manages the Icepod console.
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Output on the Icepod control panel. This particular display shows readings from the magnetometer.
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Nick and Dave monitor one gravimeter while Fabio and Grant monitor another. We have two onboard in order to compare a new one with a well-established and well-understood one.
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Gravity anomalies in real time.
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The NY Air National Guard crew is very friendly and helpful.
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Back on the ground we start to dig into the data to see what it means.

Gravity and magnetism

The IcePod focuses on properties of the ice shelf.  We also measure tiny variations in the earth’s gravity and magnetism to learn about the surface of the earth that lies hidden beneath the ice shelf.

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The gravimeters in the tent. On the left is the ZLS gravimeter, in the middle is the IMAR, and on the right is the DGS gravimeter.
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A forklift moves the pallet holding the gravimeters out to the LC-130.
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Dave surveys to determine the precise position of the gravimeters in the hold of the plane.

 

 

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Time to install the IcePod!

We finally get the word that we will get an airplane dedicated to flying the ROSETTA mission!

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There are 4 LC-130 Hercules transport planes here. We are assigned to tail number 91, the City of Alba

The LC 130 have a SABIR (Special Airborne Mission Installation and Response) arm, which allows attachment of specialized instrumentation packages like the IcePod.

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Dave, Nick, and Tej position the IcePod beneath the SABIR arm.
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Nick looks out of the bubble window to check on the progress of the IcePod installation.

The IcePod is controlled by electronic equipment that is installed in a custom-build rack that fits perfectly against the curved inside wall of the airplane.

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Nick checks the installation of the control equipment inside the plane.

So what does the IcePod do?  It provides a top-to-bottom view of the ice shelf.  First, it has visible and infrared cameras that take images of the surface of the ice shelf.  It has a scanning LIDAR, which shines a laser beam on the surface of the ice shelf and measures the time it takes for the laser light to reflect back, which allows us to measure the height of features on the surface of the shelf.  It has a shallow ice radar, which emits a powerful radio signal that penetrates into the ice, and it listens for the reflections, which tell us about different layers of snow and ice in the upper part of the ice shelf.  There is also a deep ice radar, which is at a different radio frequency, and penetrates to the bottom of the ice shelf, telling us where the bottom of the ice shelf is in contact with seawater.  Finally, there is a navigation system to tell us very precisely where we are so that we can make accurate maps of the ice shelf.