A Fourth WAAS Satellite Coming

Articles about GPS, GLONASS, GALILEO, WAAS and other satellite navigation systems
jimh
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A Fourth WAAS Satellite Coming

Postby jimh » Fri Dec 09, 2016 2:55 pm

I just noticed that a recent satellite launch for a geo-stationary earth orbit (GEO) satellite heading for equatorial position 117-W-longitude includes a hosted payload for the FAA WAAS service. Here is information from the satellite operator:

EUTELSAT 117 West B also features a payload for Raytheon to enable the U.S. Federal Aviation Administration (FAA) to increase GPS signal accuracy from 10 metres to 1-2 metres, thereby enhancing aviation safety for users in Canada, Mexico, Puerto Rico and the continental United States including Alaska. The WAAS (Wide Area Augmentation System) payload on EUTELSAT 117 West B is the first to be included on an all-electric satellite.


The satellite was launched in June 2016, but it will take about seven months to transition from its initial insertion orbit to its final geo-stationary orbit:

EUTELSAT 117 West B’s electric propulsion system will now be prepared for orbit-raising that is scheduled to start on 18 June and last for approximately seven months. The satellite will then undergo in-orbit tests prior to commercial entry into service at 117° West in Q1 2017.


Cf.: http://news.eutelsat.com/pressreleases/ ... ce-1442707

Assuming all goes well, the FAA SBAS constellation of satellites will then grow to four. The orbital positions will then be:

98-W on Inmarsat-4 F3
107.3-W on Anik F1R
117-W on EUTELSAT 177 West B
133-W on Galaxy 15

This gives about 10-degree longitude spacing over the lower-48 states, and then 133-W for Hawaii and Alaska coverage. Having four satellites in the WAAS SBAS constellation should increase availability. The 117-W location should also give Alaska (and other far Northwest users) added redundancy in coverage at better look angles.

The description of "electric propulsion" refers to use of an ion-drive instead of chemical propellants. The Boeing-built satellite is quite interesting. Read more at

http://spaceflight101.com/falcon-9-eute ... 17-west-b/

The name Satmex 9 is also used to describe this satellite. This is apparently a reference used by the satellite operating company SATMEX, which was taken over by EUTELSAT in 2014.

A "hosted payload" means the satellite operator, usually a commercial company, agreed to take along someone else's gear on the space vehicle. The hosted payload fits onto the satellite platform, uses the electrical power of the satellite system, and possibly some of the communication faciliteis of the satellite, but performs its own function, separate from the satellite's primary payload. It is quite common for commercial operators of satellites in geostationary earth orbit to offer this service, particularly to government customers. All the WAAS signals-in-space segment transponders are hosted payloads aboard commercial GEO satellites operated by private companies.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Mon Dec 12, 2016 9:01 am

Note that the Air Force has already assigned a PRN code for a space-based augmentation system (SBAS) for a GEO satellite at 117-W. According to their PRN assignment list at

http://media.defense.gov/2016/Jul/22/2001580805/-1/-1/1/L1%20C-A%206%20JAN%2016.PDF

the PRN code 131 is to be used at for this satellite.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Wed Dec 14, 2016 2:41 pm

To sum up information on the present WAAS signals-in-space and what is anticipated to be a new signal in the near future, here is a listing going from East to West:

Satellite       MNEA       PRN        GEO Slot

INMARSAT-4F3 NMEA-46 PRN-133 98.5°W
(AMR)

ANIK F1R NMEA-51 PRN-138 107.3°W
(CRE)

SATMEX9 NMEA-44 PRN-131 117°W
(EUTELSAT 117 West B)

GALAXY-15 NMEA-48 PRN-135 133°W
(CRW)


SATMEX9 won't be in final orbit until early 2017. Exactly when it will be available as part of WAAS remains to be discovered.

Exactly how present-era GPS receivers will utilize a WAAS signal at PRN 131 is also going to be interesting. A few years ago I owned a GPS receiver with WAAS, but when the existing satellites at that time were replaced with new signal sources having different PRN codes, the WAAS function stopped working on that older receiver. How more recently made GPS receivers react to a WAAS signal from PRN 131 will remain to be seen.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Thu Dec 15, 2016 10:57 am

According to a presentation from the FAA made in September 2014, facilities for WAAS signals-in-space are under contract as follows:

--AMR (INMARSAT-4 F3 PRN133) completed the base contract in November 2015, and has options to continue until November 2017 (which apparently have been exercised as it is still in service, although in a back-up role. It does not broadcast a ranging signal.)

--CRW (GALAXY 15 PRN 135) base contract will end July 2017. (It is in primary service, sending both correction signals and a ranging signal.)

--CRE (ANIK F1R PRN 138) base contract will end July 2017. (It is primary service, sending both correction signals and a ranging signal.)

--A contract awarded in 2012 to Raytheon provided for development of a new WAAS payload, generic name GEO5. (This payload is now aboard SATMEX9, launched in June 2016, and is on its way to GEO orbit at 117-West, arriving on station in early 2017.)

Following that 2014 presentation, there was an announcement in 2015 of a contract award to Raytheon for development of a new WAAS payload (generic name GEO6) and two additional ground uplink stations. The plan calls for GEO6 to be operational by early 2019. The FAA plan also calls for development of a GEO7 to begin in 2019.

Thus in 2017 we will have a number of events occurring that relate to WAAS. The base contract or option years for the three currently operating WAAS payloads will end. SATMEX9 should be ready for service, and GEO6 (whose host is not yet designated) should be ready for launching.

The FAA WAAS system calls for two satellites to always be available. In order to provide a 99.98-percent availability of continuity of at least two GEO sources, three satellites in orbit are needed. When the WAAS constellation has only two satellites available, there is single point of failure if one of them fails. Since replacement of a GEO is considered to take four to five years, if one satellite failed a system with only two satellites would have a catastrophic loss of service. This is the basis for the operating plan to maintain three satellites. It will be interesting to see which satellites contracts are extended. An FAA publication in 2015 states that GEO5 and GEO6 will replace current operational satellites nearing the end of their lease terms. It appears all the leases will be up for renewal in 2017, and exactly which ones will end remains to be known.

CRW or GALAXY 15 was launched in 2005 and has an anticipated lifespan of 15 years (to 2020).

CRE or ANIK F1R was launched in 2005 and has an anticipated lifespan of 15 years (to 2020).

AMR or INMARSAT-4 F3 was launched in 2008 and has an anticipated lifespan of 13 years (to 2021).

The orbital position of GALAXY 15 at 133-W is particularly useful for maintaining coverage to Alaska, so that may portend its contract will be extended.

Looking even further ahead, the FAA published a "market survey" inquiry to potential satellite builders and operators regarding future GEO hosted payload suppliers. In their survey, the FAA asked:

Does your company expect to participate in the launch and operation of Geostationary Earth Orbit (GEO) satellites over North America between 2017 and 2022? The orbital arc of interest for the FAA is from 115 to 137 degrees West longitude, with a strong preference for 119 to 129 degrees West longitude.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Sat Mar 04, 2017 10:57 am

The illustration below shows coverage footprints of the four WAAS SBAS sources anticipated to be in service by late 2017. The green trace is the footprint of the newest satellite SATMEX 9 at 116.8-W longitude in geo-stationary orbit.

FAA_WAAS_Coverage2017_783x692.jpg
WAAS SBAS Satellite Footprints; from FAA Presentation
FAA_WAAS_Coverage2017_783x692.jpg (76.68 KiB) Viewed 3413 times


Although the signals from these satellite can be received over a very wide area, users must recognize that the augmentation data they provide is only useful in the specific regions of North America which are shown in the illustration as a shaded polygon.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Wed May 10, 2017 1:05 pm

The following press release from satellite operator EutelSat announced the arrival of Eutelsat 117 West B to final geostationary orbit position following a seven month long transition orbit and initiation of commercial services. Note that operation of the FAA WAAS transponder is said to be scheduled for 2018:

--begin press release---
Paris, 16 January 2017
Eutelsat Communications announces that its EUTELSAT 117 West B satellite has entered into full commercial service and is now ready to support customers across Latin America.

Commercialised by the Eutelsat Americas affiliate, EUTELSAT 117 West B is the second all-electric satellite in Eutelsat’s fleet. It is equipped with 48 Ku-band transponders (36 MHz equivalent) connected to four beams providing premium coverage of Mexico, Central America and the Caribbean, the Andean region and the Southern Cone. Eutelsat’s new satellite complements EUTELSAT 117 West A, launched in 2013, to create a multi-satellite neighbourhood at 117° West, which is already used by Millicom’s Tigo Star, Stargroup and Televisa. It will also provide key services to telecom operators and government service providers in Latin America.

EUTELSAT 117 West B also features a new-generation WAAS (Wide Area Augmentation System) payload operated by Raytheon as prime contractor for the U.S. Federal Aviation Administration (FAA), which will go live in 2018. Developed for the civil aviation community, the WAAS payload is designed to receive signals from ground stations that verify signal accuracy and rebroadcast the information to GPS users, including airline cockpits, the most demanding of civil GPS applications. It will increase GPS signal accuracy from 10 metres to 1-2 metres, thereby enhancing aviation safety for users in Canada, Mexico, Puerto Rico and the continental United States including Alaska.

The WAAS payload is the first to be hosted on an all-electric satellite. It is also the third hosted payload on a Eutelsat satellite, following the EDRS-A data relay node on EUTELSAT 9B for ESA and Airbus Defence and Space and the S-band payload on EUTELSAT 10A for Echostar.
--end press release--

Source: http://news.eutelsat.com/pressreleases/eutelsat-117-west-b-all-electric-satellite-fully-charged-and-now-in-commercial-service-1744939


Based on information from the satellite-oriented website SATBEAMS.COM, it appears that Eutelsat 117 West B (formerly called SATMEX9) has some of its transponders operational. See

https://www.satbeams.com/satellites?norad=41589

With the satellite on station at its assigned location, testing of the SBAS transponder for the FAA's WAAS should be coming soon. I haven't seen any public announcements from the FAA about the status.

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Fri Sep 15, 2017 6:01 pm

On the main webpage at

http://www.nstb.tc.faa.gov/

It says the following

NOTICE: GEO PRN 133 (AMR) will be removed the from the WAAS satellite mask in November 2017, and will cease broadcast until further notice.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Sat Sep 16, 2017 7:54 pm

That PRN 133 will stop transmitting is quite interesting news. That satellite was in the best position for eastern USA users. For users on the ground (or on the water) in the eastern USA, PRN 133 has had the highest look angle and thus the best signal. The FAA must be planning to bring on-line another satellite to replace PRN 133.

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Fri Sep 22, 2017 12:58 pm

This document mentioned that EUTELSAT-117WB, would be in service in Oct 2017.

http://www.gps.gov/multimedia/presentat ... rence1.pdf

Yet they say at

http://www.eutelsat.com/en/satellites/E ... 117WB.html

It will enter service for WAAS, in 2018.

At least two months ago, EUTELSAT-117WB once showed up as a " 44 " on my Magellan receiver. My Garmin 16 OEM receiver won't show it, but when reset all the other WAAS satellites show up.

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Fri Sep 22, 2017 1:01 pm

I wait for EUTELSAT-117W to show up [on the near real-time status page]: http://www.nstb.tc.faa.gov/rt_waassatellitestatus.htm

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Sat Sep 23, 2017 6:26 am

I believe that the WAAS transponder "AMR" carried on INMARSAT-4 F3 at 98.5-degree W longitude and assigned PRN 133 had two drawbacks, which probably account for its short service life:

--AMR PRN-133 was not sending a ranging signal; the other two WAAS transponders are sending a ranging signal and are often used in position solutions by GPS receivers; and

--AMR PRN-133 had no L5 capability; the WAAS system is transitioning to dual frequency operation using L1 and L5 carriers.

Some earlier FAA documents show that AMR PRN-133 was operational in 2008 and expected to have a service life of 13 years, perhaps to 2021. However, as the transponder was operated under a lease agreement, the FAA apparently intends to end the lease arrangement this year.

The report of PRN-131 showing up (as NMEA 44) is quite interesting. I will have to check my GPS receiver more closely in the next few weeks to see if there is any sign of PRN-131 being received. It has been my experience with some older GPS receivers that they are not particularly agile about hunting for new signals at unusual PRN numbers in the SBAS range of numbers. I had a c.2003 GPS receiver that was working with the WAAS signals of that epoch, but when the FAA brought new satellites into service with new PRN numbers, that old receiver was never able to work with them.

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Sat Sep 23, 2017 6:02 pm

I have attached a screen capture, showing EUTELSAT-117W on my GPS receiver display as a [NMEA number] 44 and also as a "W" which means the receiver is picking up a signal from a WAAS satellite. I was suprised, to see the EUTELSAT-117W showing up on the display.

I was using a Magellan Explorist 110 at the time.
Attachments
44.png
44.png (14.42 KiB) Viewed 2692 times

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Mon Sep 25, 2017 9:12 am

Seeing a new WAAS signal at PRN-131 (MNEA 44) is very interesting. Thanks for providing the screen capture of satellites in view.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Wed Oct 25, 2017 9:37 am

Regarding whether older GNSS receivers will be able to use the new WAAS signal coming from PRN-131:

I came across some information I received from Lowrance regarding the GPS receiver in my first-generation HDS-8 chart plotter. According to Lowrance the receiver "automatically searches [PRN] 120 to 138 one by one and uses the [source] with the best signal strength." This suggests that there won't be any operational problem for the HDS-8's GPS receiver to use the newest WAAS satellite. Unfortunately, the HDS-8 satellites-in-view display does not always identify the WAAS satellite it is using. It seems to identify the satellite by PRN if it is using it in a position solution, and since PRN 135 and PRN 138 are also sending ranging signals, they sometimes show up on the graphic display.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Sat Nov 04, 2017 10:21 am

The FAA has shut down the SBAS signal PRN 133 originating from satellite INMARSAT-4F3 at 98.5°W. This signal was always a bit different than the two other SBAS signals. The signals from PRN 135 and 138 included pseudo-ranging signals in addition to correction data, allowing those satellites to be used in position solutions. There was no pseudo-ranging signal from PRN 133.

There is speculation that the reason for no ranging signal from the PRN 133 satellite was due to the geostationary orbit of INMARSAT-4F3 not being as well controlled as the other satellites. At the moment the orbit of INMARSAT-4F3 has an inclination of 3.0268-degrees; the other two satellites have inclinations of 0.0043-degrees (ANIK F1R) and 0.0100-degrees (GALAXY-15). (Data from http://www.satellite-calculations.com/Satellite/satellitelist.php )

You can see plots of the apparent motion of the INMARSAT-4F3 satellite orbit at

http://www.satellite-calculations.com/S ... 71/0/33278

These plots show that over a 24-hour period the satellite has quite a bit of movement in all three planes. This may have made use of this satellite for a ranging signal to be more difficult than the other satellites, which show much less apparent motion in their orbits.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Mon Dec 25, 2017 7:20 am

The GPS ALMANAC now shows that WAAS signal with PRN 131 from Eutelsat 117W B "Has begun test transmissions."

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Tue Apr 03, 2018 7:57 pm

On the main webpage at

http://www.nstb.tc.faa.gov/

It says

NOTICE: GEO PRN 131 (SM9) came online March 27th, 2018.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Wed Apr 04, 2018 8:11 am

Great news. Thanks for catching that announcement.

"SM9" must refer to SatMex 9, the former name for the Eutelsat 117W B satellite before the satellite operator SatMex was taken over by EutelSat.

The PRN 131 is also now shown in green (Precision Approach) status at

http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm

I believe that this status indicator means that the source is sending a ranging signal as well as an augmentation signal. I will check with my GNSS receiver to see if it picks up PRN 131 as a ranging source.

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Re: A Fourth WAAS Satellite Coming

Postby jimh » Thu Apr 05, 2018 8:35 am

My GPS receiver was on all day at home, with a good view to the West and Southwest, I checked the Satellites-in-view screen frequently, looking for evidence of Eutelsat 177W B to show up. After several hours, PRN 131 appeared.

HDS_SatViewPRN131.png
HDS-8 Satellites In View screen shows PRN 131
HDS_SatViewPRN131.png (28.21 KiB) Viewed 839 times


In the polar plot of azimuth and elevation to the satellites, PRN 131 is not marked in blue. I believe this means it is not being used in the pseudo-ranging solution. Generally the WAAS satellites don't always show up in the satellites-in-view screen on the HDS. I don't have a good theory for why they don't always appear. The cause might be due to having a limited number of resources allocated to displaying the signal-strength (which is actually carrier-to-noise density and not signal-to-noise ratio); it seems only about ten grow bars can be shown. This might mean that the SBAS satellite will only be displayed when there are less than ten other satellites in view. That only happens at certains times in particular locations. Frequently at my latitude there are more than ten ranging satellites in view at once.

I should also mention that on some GNSS receivers the display of satellites-in-view will be shown with satellite "NMEA numbers" instead of the actual PRN numbers. The NMEA number corresponding to PRN=131 will be NMEA=44. (In NMEA-0183 the specification only allows for two-digits for the satellite PRN so an awkward workaround was implemented; subtract 87 from the PRN to identify SBAS sources.)

In the HDS-8 there is no positive indication for exactly which SBAS source is being used for the augmentation. The satellites-in-view page will often show that WAAS augmentation is being used but not show any PRN for a WAAS SBAS source. In the screen shot above, I just infer that a satellite sending as PRN=131 was being received and tracked by its appearance in the polar plot, but I cannot tell with certainty that the augmentation from PRN 131 was in use. It is also a bit odd that the satellite was not marked in blue. As I mentioned earlier, on the WAAS real-time status page PRN 131 is shown with an indicator that its pseudo-ranging signal can be used for precision approach by aircraft. It may be that the HDS-8's GPS receiver just doesn't use SBAS sources for any ranging solutions.

It is encouraging that the HDS-8 GPS receiver was able to find and track PRN 131. This shows that the receiver was not hard-coded to look only for certain PRN numbers in the SBAS range. (SBAS sources use PRN identities in a particular range, from 120 to 138, with expansion to 158 possible.)

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Re: A Fourth WAAS Satellite Coming

Postby kfetter » Thu Apr 05, 2018 11:07 am

It showed up on my GARMIN GPS-16x receiver, as a "44 "

44.jpg
Satellites in view from GARMIN GPS-16x
44.jpg (134.44 KiB) Viewed 825 times