SAR Satellite FlyBy and Successful Rendezvous

Day: 18 — Position: N21 13.7’ W170 43.9’
Odometer since Waikiki: about 731M
Distance to Northern Marianas: 2,489M
Water temperature: 81.3F - 27.4C

OCEAN ROWING RECORDS AS RUNNING TOTALS
Solo career total in days by Waikiki: 925 now 943 (New World Record)
Overall career total in days by Waikiki: 1,009 now 1027 (New World Record)
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Solo career total in miles by Waikiki: 22,173M now about 22,904M
Overall career total in miles by Waikiki: 25,153M now about 25,884M
** Ralph Tuijn (NL) leads this with 35,635M

The numbers by the time I reached Waikiki are as recorded in the Ocean Rowing Society database. ORS will adjudicate the additional time and distance that I will have rowed to my point of landfall on mainland Asia then append those to my career totals.

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Yesterday I successfully achieved a rendezvous with the Sentinel-1 SAR satellite. As the satellite flew by, it was scheduled at 25OCT2021 05:20:29UTC to take a 20km by 20km image the center of which was at N21 12.6’ W170 27’.  This was just around dusk on the 24th local time.

SAR stands for “synthetic aperture radar.” This satellite sends a 5cm wavelength microwave beam at the Earth’s surface then captures and analyzes the back scatter. As such, it can capture an image without the need for daylight and without any hindrance from cloud cover. My mission was to be inside that 20km x 20km image at the time the satellite was scheduled to snap the shot. You can think of this as a target with a 5.5M radius around the center. I was at 0.94M east of center at the time of my rendezvous, which is as close to a bull’s eye as one can bring my low horsepower vessel which cannot be stopped. 

Knowing that the outcome of our experiment was greatly influenced by currents and winds, I had to rely on information on currents that my friend Jason Christensen provided. That is why you saw my course descend SW on the 20th in anticipation of a northerly current that I would later encounter beginning on the 22nd.

I slept 5 hours then woke up at 02:30 boat time yesterday. There was a squall to my south passing east to west which created strong winds which pushed my boat NW. I waited about 30 minutes in the cabin for that to move on while fixing coffee then began my long day. 

The boat was very well positioned upwind of the target location of image center. There was no question that I was going to pass over the target. The question was whether I could pace myself to be within a 5.5M radius of the same at the time of my rendezvous. 

So began my hourly monitoring. At every 20 minutes past the hour, I would take the distance remaining to the target then subtract 5.5M and divide that number by the whole number of hours remaining. This would give me the minimum average speed to maintain. I would repeat that by adding 5.5M to obtain the maximum average speed. With the seas in my favor, I kept a decent pace and as the remaining distance diminished, my window on speed began to widen to the point where I could stop rowing and simply work my rudder to keep my rowboat on course.

About 5 minutes before the rendezvous, I changed my tracker to transmit my location from every 15 minutes to by the minute. Then during the two minutes spanning the scheduled time, I was transmitting my location every 15 seconds. I continued by the minute for another short while then reset the tracking to four times an hour. I was told that the Sentinel-1 satellite would pass from my SSE to my NNW at 24 degrees above my horizon. In order to present the satellite a larger aspect of my rowboat, I set her on starboard tack which pointed my bow to about WNW. At the time of scheduled rendezvous I was 0.94M east of image center, which is bull’s eye given the circumstances. I was also asked to describe the sea state and cloud cover then provide pictures of the same. I submitted four images of the horizon, one for each cardinal direction.

We will see if the YoHI team can locate my rowboat on the SAR image. This collaboration with researchers Nicolai Maximenko, Jan Hafner and Justin Stopa at the University of Hawaii, provides them “ground truthing” of what is digitally presented. Comparing results with a known object such as my rowboat, other applications may be possible including large tsunami debris tracking, surveillance of fishing or other activity, finding lifeboats in a search and rescue situation.

This is another example of collaboration with scientists, further justifying the Flag Expedition status for this row across the Pacific Ocean. I was issued the storied Flag #97 with its own documented history of expeditions. My own expedition report after my landfall on mainland Asia will append to that history.

Erden.