Despite the delays in the launch of GX, it seems Inmarsat may be looking to stitch up an even larger share of the maritime market in the near term. Rumors are flying that Inmarsat may soon make a formal bid to acquire KVH, the largest maritime VSAT player in terms of vessels (though not in revenues), adding about 3500 more terminals to Inmarsat’s existing 2200 VSAT equipped ships.
KVH generated nearly $80M from its miniVSAT business in 2014 with an average service ARPU of $1500 per month, compared to Inmarsat’s $90M and ARPU of $4000 including equipment leases (this equates to $2500 per month after stripping out hardware, according to Inmarsat’s most recent results call, which is a more appropriate point of comparison with the KVH ARPU).
The difference in ARPUs between Inmarsat’s current VSAT business and KVH is striking, in fact KVH’s smaller V3 terminal (which has about 900 active terminals) is generating around $500 in monthly ARPU, below even Inmarsat’s FleetBB ARPU of $700 (note that the standard FleetBB package sold by KVH now only provides 20 Mbytes per month of data for $749, whereas KVH offers airtime at rates as low as $0.99 per Mbyte).
If Inmarsat does move ahead with a KVH bid, it would likely be seen as a counter to Airbus’s disposal of its Vizada business unit, because Inmarsat would then have by far the largest number of VSAT-equipped ships. Indeed it would not be surprising to see attempts by competitors to block the deal on antitrust grounds, not to mention the concerns that current KVH customers will have about potential future price increases.
However, it would also be something of an acknowledgement that GX is optimally positioned as a lower end off-the-shelf maritime VSAT service (like KVH’s miniVSAT), as a step up from FleetBB, rather than as a high end solution for cruise ships and oil rigs. KVH’s growth has slowed in the last year, with terminal shipments staying at close to 1000 per year in 2012, 2013 and 2014, but net adds and ARPUs declining. Pressure from Inmarsat will only intensify, once the low cost 60cm GX antenna is available with global coverage, so this looks like it would be a good time for KVH to sell out.
Inmarsat investors will presumably also welcome a deal, with a much clearer path established to a GX maritime business of $200M+ in annual service revenues over the next few years (though its important to note this represents a retail service business, not the wholesale spend on satellite capacity). However, the obvious question that customers will ask is whether low end price packages will still be offered for miniVSAT users, or whether Inmarsat will move them up to much higher price points, as it has done with FleetBB over the last few years.
And what will be the alternative for these users: will it be other VSAT solutions, or will it be the new broadband services (comparable in capability to FleetBB) offered by Iridium’s NEXT constellation? It will take some time for either of these options to emerge, with low cost small Ku-band VSAT antennas needed for the former, and completion of the NEXT constellation needed for the latter. That provides a further motivation for Inmarsat to move sooner rather than later, while its freedom of action in the low end of the maritime market remains relatively unconstrained by competitive alternatives.
If I’m right and DISH is determined to win a significant AWS-3 spectrum position at the end of the auction, then it seems highly likely that one or both of AT&T and Verizon will leave the auction with a significant shortfall in AWS spectrum in major cities including New York, Los Angeles and potentially several other markets.
Then it seems Ergen’s calculation is that he will have significant leverage to force AT&T and Verizon to deal with him and lease spectrum on his terms (including supporting interoperability for his AWS-4 spectrum holdings). However, one way for AT&T and Verizon to freeze Ergen out and avoid having to make a deal would be for them to instead purchase 2.5GHz spectrum from Sprint. Its plausible that Sprint could raise as much as $10B relatively easily from selling say 30MHz to each of AT&T and Verizon, leaving Ergen holding an asset with no clear route to monetization and a buildout deadline which will start to become a pressing concern within a year or two (especially if DISH has not yet standardized the AWS-4 band).
So does Masa Son want to boost DISH’s position at the expense of AT&T and Verizon, or would he like to get revenge for DISH’s actions in the Sprint & Clearwire bidding wars last year? If DISH is stuck with billions of dollars of spectrum it can’t lease, then DISH will be disadvantaged in mounting a competing T-Mobile bid, when Sprint renews its attempts after the 2016 Presidential election, because DISH will struggle to raise as much cash and DT will be reluctant to accept shares whose value is based primarily on spectrum assets with limited utility (remember that T-Mobile isn’t in a position to create an ecosystem for AWS-4, unlike AT&T and Verizon).
In fact, Sprint could point to DISH’s reserves of spectrum as providing the basis of a new competitor in the wireless market, and could even gain the tacit endorsement of AT&T and Verizon for a purchase of T-Mobile. In addition, by selling some spectrum now, Sprint raises money to participate in the 600MHz incentive auction (where DISH may not have the resources to compete) and gets out from under the spectrum screen limitation. So it might well make sense for Masa to make a choice which boosts AT&T and Verizon, rather than cooperating with DISH.
Incidentally, another side-effect of the AWS-3 auction prices is that Phil Falcone is now scrambling to get back into the LightSquared reorganization plan, as his argument that LightSquared’s spectrum should be valued at more than the debt gains support from these price benchmarks. For example, the unpaired uplink 10MHz B1 block (1700-1710MHz), currently valued at almost $1.3B, will be used to argue that LightSquared’s two 10MHz uplink blocks alone are worth double this sum. So the obvious counterstrike from Ergen is likely to be to try and blow up the reorganization plan and force LightSquared into liquidation.
I understand conversion to Chapter 7 would invalidate the Inmarsat Cooperation Agreement, and thereby make it much harder for anyone to take on the risk of buying LightSquared’s assets. Of course, that is unlikely to worry Ergen (he would be expected to take a hard line with Inmarsat in any case), and would provide an opportunity to potentially buy LightSquared’s satellite assets for considerably less than the value of the LP debt and boost Ergen’s attempts to corner the spectrum market. As one person close to the case told me, such an outcome would literally make Judge Chapman cry.
UPDATE (11/26): Another interesting question is the status of the 650M MHzPOPs of EBS spectrum (38MHz) that NextWave holdco controls in New York City. I would expect hectic bidding to secure access to that spectrum, if DISH turns out to be the winner of much of the AWS-3 spectrum in New York. Of course, Ergen has likely already thought of that, and I’d speculate that he might even have locked up an agreement to buy that spectrum block in advance of the AWS-3 auction, making it harder for Verizon and AT&T to address their potential spectrum shortfall in the New York market.
The independent group analyzing the loss of MH370 has now issued a new statement, responding to the release of the June 26 ATSB report.
After the NTIA filed a fairly devastating letter with the FCC on July 1 (which went completely unnoticed in the press), it seems that Phil Falcone decided to use the July 4th holiday to assert his own independence from LightSquared, and attempt to blow up both the company and its relationship with the US government.
The NTIA letter attaches a September 2013 letter from the Department of Transportation, which states that “the Department questions whether the Commission has the necessary and sufficient information before it to approve the handset proposal at issue in the Public Notice. Again, to the Department’s knowledge, there has not been any robust interagency effort to examine or test LightSquared’s proposal, to probe the underlying assumptions, or to consider feasible alternatives.” The NTIA states that “the agencies are not in complete agreement that the Uplink Assessment has adequately addressed these issues to support a recommendation to NTIA and the FCC” and “NTIA agrees with DOT that the FCC should seek to ensure that LightSquared’s handset proposal is adequately supported by data and a full understanding of the potential impacts on GPS receivers.”
This letter comes in conjunction with the June 20 FCC workshop, which appeared designed to demonstrate that the FCC was seriously investigating whether interference concerns could be resolved, but was structured in a manner that was very supportive of GPS. It also immediately follows LightSquared’s proposal of a new plan for emergence from bankruptcy, which is supposed to be filed with the court on Monday July 14. The NTIA letter means that there is no clear roadmap even to approval of the 20MHz of uplink spectrum that LightSquared assumes is certain to be available, significantly undermining the foundations of the new plan.
More importantly, Falcone’s actions over the last week basically destroy any prospects of further progress with the FCC. While his RICO lawsuit against Ergen and DISH can be largely ignored, the decision to sue the US government and FCC on Friday, is expected to freeze further contacts with the FCC while the lawsuit is in progress.
The likely way forward is now for LightSquared to sue Harbinger in order to prevent the lawsuit going forward, since such lawsuits would normally be regarded as assets of the bankruptcy estate, belonging to LightSquared rather than its shareholders. Harbinger alleges that all negotiations with the FCC prior to the March 2010 takeover were directly with Harbinger’s lawyer (Henry Goldberg), not “LightSquared” (at that time SkyTerra) but it is far from clear that would overcome the presumption that the claims belong to LightSquared.
In any case, the names of the underlying companies changed after the Harbinger acquisition: what is now LightSquared Inc. was at that time Harbinger Global Wireless (HGW), which was the company (represented by Goldberg) that was formally given permission to buy SkyTerra. So even if there was an agreement with HGW (which is doubtful), its claims should now belong to LightSquared Inc. and the bankruptcy estate.
There are several other curious statements in the lawsuit, most notably that the publication of the National Broadband Plan in 2010 was delayed to coincide with the Harbinger acquisition of SkyTerra. Secondly, the amount of Harbinger’s losses was set at $1.9B, but that is far in excess of the amount of investment that Harbinger made in LightSquared after March 2010. Finally, the concept that there was an agreement with Harbinger under which the ATC modifications were granted in exchange for the commitments made as part of the takeover is not part of the formal record: the ATC mods order (which Harbinger claims the FCC has not upheld) is completely separate from the approval of the takeover (which included the Harbinger commitments).
Overall, this marks a significant change in the bankruptcy case: Falcone is on the outside rather than the inside, and now it seems quite likely that the entire new plan will collapse in acrimony. Moreover, the company is on the verge of running out of cash, creating a further crisis in the very near future.
UPDATE (7/15): Yesterday LightSquared’s Special Committee finally recognized the reality of the situation by reaching an agreement with Charlie Ergen to convert his existing debt into a dominant share of the new first lien debt, and obtain an additional $300M first lien loan, replacing JP Morgan in the new capital structure. It was stated that there will be $1.6B of new first lien, with $1.3B from Ergen, and I would assume the remaining $300M will come from Fortress rolling over its first lien debt. Its unclear if Cerberus will also invest in the new second lien tranche, and it certainly seems highly implausible that Harbinger will accept its proposed treatment under the new plan, since this would bar Harbinger from asserting claims against the FCC or Ergen, and therefore the probability of any recovery for Falcone is significantly diminished. It therefore seems highly likely that, as I predicted, the next stage of the bankruptcy case will be litigation between LightSquared and Harbinger, while Ergen just has to sit back and enjoy Phil Falcone’s discomfort.
Last week’s Wall St Journal article and my blog post highlighted that the MH370 search area was poised to move to the southwest, and yesterday this shift was confirmed by Inmarsat.
Although the location of this new search area has not yet been released, the independent team that has been analyzing the publicly available data felt it was appropriate to provide a statement, given below, with our best estimate of the highest probability (but not the only possible) location for a potential search. In this way, we hope to provide information which can clearly be seen to be completely independent of any locations that might be published by the search team in the near future.
The statement is as follows:
Shortly after the disappearance of MH370 on March 8th, an informal group of people with diverse technical backgrounds came together on-line to discuss the event and analyze the specific technical information that had been released, with the individuals sharing reference material and their experience with aircraft and satellite systems. While there remain a number of uncertainties and some disagreements as to the interpretation of aspects of the data, our best estimates of a location of the aircraft at 00:11UT (the last ping ring) cluster in the Indian Ocean near 36.02S, 88.57E. This location is consistent with an average ground speed of approximately 470 kts and the wind conditions at the time. The exact location is dependent on specific assumptions as to the flight path before 18:38UT. The range of locations, based on reasonable variations in the earlier flight path result in the cluster of results shown. We recommend that the search for MH370 be focused in this area.
We welcome any additional information that can be released to us by the accident investigation team that would allow us to refine our models and our predictions. We offer to work directly with the investigation team, to share our work, to collaborate on further work, or to contribute in any way that can aid the investigation. Additional information relating to our analysis will be posted on http://duncansteel.com and http://blog.tmfassociates.com. A report of the assumptions and approaches used to calculate the estimated location is being prepared and will be published to these web sites in the near future.
The following individuals have agreed to be publicly identified with this statement, to represent the larger collective that has contributed to this work, and to make themselves available to assist with the investigation in any constructive way. Other members prefer to remain anonymous, but their contributions are gratefully acknowledged. We prefer that contact be made through the organizations who have published this statement.
Brian Anderson, BE: Havelock North, New Zealand;
Sid Bennett, MEE: Chicago, Illinois, USA;
Curon Davies, MA: Swansea, UK;
Michael Exner, MEE: Colorado, USA;
Tim Farrar, PhD: Menlo Park, California, USA;
Richard Godfrey, BSc: Frankfurt, Germany;
Bill Holland, BSEE: Cary, North Carolina, USA;
Geoff Hyman, MSc: London, UK;
Victor Iannello, ScD: Roanoke, Virginia, USA;
Duncan Steel, PhD: Wellington, New Zealand.
Since the Inmarsat ping data was released almost two weeks ago, I like many others have spent a good deal of time trying to discern what the data tells us. Particular thanks are due to Duncan Steel, Victor Iannello, Mike Exner, Don Thompson, Bill Holland and Brian Anderson, who’ve spent days and weeks performing numerous complex calculations and analysis of satellite and other data, much of which I’ve relied on in my analysis.
Although the data analysis remains a work in progress, and further information is needed to validate the BFO model in particular, I’ve now written up my initial conclusions, which indicate that the search area may need to be widened significantly beyond the areas identified in the most recent search effort. As the WSJ is reporting, this appears to be the approach now being taken by the investigative team.
Today’s ruling from Judge Chapman on the LightSquared bankruptcy case took four hours to read from the bench, and has not been issued as a formal order, apparently to give the parties involved until to negotiate and find a settlement, before they are ordered to mediation under Judge Drain. However, the oral ruling effectively sets out the parameters for that negotiation, most notably that part of SPSO’s debt is subject to subordination, and though SPSO may be treated differently than other secured debtholders, it may not be discriminated against. Though the judge apparently found Moelis’ valuation more appropriate than that offered by SPSO’s experts, she agreed that it was not valid without FCC approval of LightSquared’s license modification requests.
This appears to be a clear invitation to LightSquared and Harbinger to buy SPSO out of the capital structure if they are prepared to wait around for FCC approval. In that case the main subject of negotiation would be how much is paid to SPSO in respect of its debt, and whether a) that is acceptable to Ergen and b) viable for LightSquared to raise in addition to the amount already contemplated in the reorganization. The judge did not determine a specific amount of Ergen’s $844M in purchases which will be subject to subordination, but did give a range of dates that should be considered: the $320M (face value) in purchases in April 2013 were said to be on DISH’s behalf (and therefore subject to subordination), the $287M bought before October 2012 would not be subordinated and the $238M in purchases between October 2012 and March 2013 might or might not be subordinated.
Moreover, it seems that the extent to which any of these purchases would be subordinated will be dependent on the actual damages caused to LightSquared through the delay in negotiations and increased legal fees associated with the case due to the delays in SPSO closing its trades. As a result it appears only a proportion of the $320M-$558M would actually be subordinated. Given that the time taken to close the bulk of these trades was around 2 months, and LightSquared’s total operating costs including interest are around $1.5M per day, it is quite plausible that the amount actually subordinated could be no more than $100M. This would mean LightSquared having to find as much as $1B (including interest) to buy SPSO out of its capital structure.
Of course, its highly unlikely that Ergen would have been prepared to accept less than the $700M he paid for the debt in the first place, but if the potential damages in the form of subordination are relatively limited, then despite Judge Chapman’s criticism of Ergen’s testimony and behavior, he is still likely to be in a very strong position. Conversely, Phil Falcone will have a much harder time coming up with a plan that will retain value for his equity holdings.
I’m also left wondering about what David Daigle of CapRe, as the biggest single LP debtholder other than Ergen (with $331M in LP debt at face value), will now do, because as Falcone indicated in an email earlier this year “I believe [D]aigle is determined to reduce our position to nothing“. An alliance between CapRe and SPSO to push a debt to equity conversion of the LP debt would probably make it all but impossible for Harbinger to retain value in the reorganization, even if as much as $300M of SPSO’s debt was subject to subordination.
Elimination of Harbinger’s position would be equally unacceptable to Falcone, and thus it seems rather unlikely that agreement will be reached in the next couple of weeks. The best bet would therefore be to assume we will be headed to mediation and yet more DIP financing from the LP holders to extend the process for a couple more months, probably ending up either in an auction with credit bids or directly in a debt-to-equity swap. That presumably means no money for Inmarsat in June. It also implies that the probability of LP debtholders getting paid out in cash with accrued interest anytime soon has also decreased significantly. However, in the medium term it may be better news for GPS, because the debtholders would probably be prepared to drop LightSquared’s current lawsuit against the GPS industry, if it helped their efforts to get the necessary approvals from the FCC.
Over the last week a great deal of useful data has been accumulating in the comments section of my previous blog post on locating satellite pings from MH370 and I’ve greatly enjoyed all the input from many dedicated contributors across various fields of engineering and aviation. If you’re visiting for the first time then you might want to read my original primer on pings first.
In this post I’m going to try to distill this information and explain what we’ve been told today, since there is still plenty of confusion out there, and address one thing that we haven’t yet been told, but which should be able to be determined from the analysis that has been conducted. Note that the diagrams shown below aren’t mine – I’ve provided links to original sources in the supporting text.
Almost immediately after the plane disappeared, Inmarsat discovered that the satellite terminal on the plane had continued sending “pings” to the satellite every hour. This was in response to the Inmarsat network checking in with each terminal that it had not seen traffic from, in order to check that it was still connected to the network, just like the cellular network checks every so often that your phone is connected. In technical terms (from the Classic Aero specification), commenter GuardedDon described it well:
The ‘ping’ is a component of the Aero-L [or Aero-H] protocol where the GES [Inmarsat's Gateway Earth Station] attempts to check the ‘log-on’ state of previously logged on but apparently idle AES [the plane's Airborne Earth Station]. The GES determines the AES to be idle if a timer ‘tG6′ expires, tG6 is obviously the hourly period.
The GES transmits to the AES over the P channel & receives over the R channel. The initial response burst on the R channel is the timing datum transmitted by the AES ±300 μs of receiving the incoming frame on the P channel. All very deterministic to give us the range to AES from satellite using the Round Trip Timing.
The delay can be measured fairly accurately, since as noted above, the timing is specified to within ±300 μs. This calculation, from PPRUNE [Professional Pilots Rumor Network], shows that the difference in round trip delay between ping arcs 1 degree apart is around 600 μs at the relevant angle for MH370. Thus the location of each arc is known to within 1 or 2 degrees, depending on whether the satellite actually measures the round trip or one way delay to the aircraft.
The arc information was released to the public on March 15 and there was some confusion at that point about why part of the arc close to Malaysia was excluded. Possibilities included:
1) that the area had been checked by radar
2) that the plane’s minimum speed would have meant it could not have been that close to Malaysia
3) that another Inmarsat satellite over the Pacific would have received the signals in this excluded part of the arc.
This issue has still not been clarified, but of these it appears that a combination of the first and second explanations is the most plausible.
Inmarsat measured the arc positions each hour from 2.11am to 8.11am and the possible routes taken by MH370 can be estimated by assuming that the plane was flying at a constant cruise speed, and then noting that the distance between the points at which the plane crossed each successive arc is equal to the distance the plane traveled in one hour. That led to the NTSB’s two potential tracks for the southern route, published by AMSA on March 18, which included two different assumptions for the speed at which the plane was flying.
Several news organization have published purported ping arcs for the intermediate ping times, including CNN and the Washington Post. However, its important to realize that these arcs are not based on real data, and are purely illustrative, like the chart produced by Scott Henderson.
What was not stated initially by Inmarsat or the investigators was that each of the hourly arcs is further away from the satellite than the previous one. In other words the plane was moving away from the satellite continuously from sometime soon after the 2.11am ping. This statement was made by Inmarsat on Friday (and I have also confirmed it). Once this sequence becomes clear, then it becomes impossible for the plane to have flown out over the Indian Ocean and later have returned to the vicinity of Malaysia. It also has significance for additional reasons that will be discussed below. As Jeff Wise noted, this means that the plane flew only between the green arc (the pink dot where it was at 2.11am) out towards the red arc where the last ping was recorded.
To be more precise, since Inmarsat has indicated that the plane was outside the green arc by 3.11am, the plane did not continue on its northwesterly course for long at all after contact was lost by Malaysian military radar at 2.22am (enabling it to return outside the green arc before the 3.11am ping). That would be consistent with avoiding Malaysian radar, but heading south the plane would have very likely crossed Indonesian radar coverage (something that the Indonesians have denied).
This sequence of ping arcs led inexorably to either a northern or a southern track, but there was still some uncertainty about which one was correct. The analysis that Inmarsat undertook over the last week took into account that the I3F1 satellite is in a slightly inclined orbit, which moves north and south of the equator each day. In other words it is only station-kept in the east-west direction, not north-south. While this situation is often the case for old FSS satellites, where the fuel is nearly exhausted, even new MSS geostationary satellites do not use strict north-south stationkeeping because the beam width of a small L-band antenna is pretty wide and so accurate pointing is not required.
DuncanSteel noted that the satellite was actually north of the equator at the time in question and Inmarsat was able to use the fact that the satellite was moving relative to the aircraft to calculate the resulting Doppler effect that shifted the frequency of the ping as measured at the satellite. If the satellite was moving towards the south, then the frequency of pings from airplanes flying in the southern hemisphere would be shifted up in frequency, while the frequency of pings from airplanes in the northern hemisphere would be shifted slightly down in frequency.
Last week Inmarsat performed an analysis of pings received from other aircraft flying in the Indian Ocean region to confirm that this effect is consistent across all of these planes and therefore concluded that MH370 must have been to the south of the satellite at the time of the last ping, not to its north. This led up to today’s announcement that the plane must have crashed in the Southern Ocean.
Now for an interesting piece of information that does not appear to have been considered in detail. A pilot on PPRUNE pointed out that there are two different modes of operation of the 777 flight management computer. A programmed route will take a straight line (great circle) route to the next programmed waypoint, but if there is no longer any waypoint in the computer, then the plane will fly on a magnetic bearing. While this is not material around Malaysia, it becomes highly significant in the Southern Ocean.
As a result, a magnetic heading would need to start out going significantly further west (and would also fly much further) to end up at the same point as a great circle route.
It is easy to see that in combination with Jeff Wise’s chart of the ping lines, a magnetic bearing heading is highly unlikely to have resulted in the 3.11am ping arc lying outside the 2.11am ping arc. Once this is realized, the hypothesis that the plane suffered an accident that left it flying on autopilot becomes rather less likely than the plane being deliberately directed towards a part of the southern ocean where presumably whoever was in charge believed the aircraft would never be found.
Indeed the NTSB tracks appear to implicitly assume an absolute not a magnetic heading, so would require the plane to be flying in a pre-programmed direction. Of course we need to see the ping arcs themselves (or at least get absolute confirmation about the trend in the ping arcs) before reaching a definitive conclusion, but this issue appears quite significant for any assessment of what might have happened onboard MH370.
UPDATE (Mar25): The Malaysia government has just released this full picture of the potential southern route tracks. The red track appears to be a magnetic bearing heading which would have required a slower speed (400 knots) and would result in a location far to the northeast of previous estimates. The yellow track is apparently the originally assumed programmed heading at cruising speed of 450 knots and is consistent with the current search area. There is clearly an enormous difference in where the plane ended up.
UPDATE (Mar25): The Doppler shift data release by the Malaysian government gives full details of the ping times (note that they are in UTC so add 8 hours for local Malaysian time which is used above). Several pings were received at just before 2.30am, then at 3.40am, 4.40am, 5.40am, 6.40am and 8.11am, not at 2.11am, 3.11am, etc as surmised above.
It seems clear from the Doppler information that the plane made a sharp turn very shortly after it was lost from Malaysian radar coverage at 2.22am. There is also much more time for the plane to move outside the 2.30am arc by 3.40am so this does not impose as much of a constraint on the possible routes of the plane.
The question has been raised about the apparent “partial” ping shortly after the 8.11am ping was recorded. Was that a partial ping because the plane lost power during the course of that handshake? Its hard to tell, but I note that there were several pings quite close together around 2.30am after the “possible turn”. Those appear to have occurred for a different reason than the regular pings (and also from the more frequent earlier handshakes after take off which I assume relate to regular ACARS messages being transferred).
So an understanding of why those occurred is likely to shed some light on why a ping might have been attempted so soon after 8.11am. In particular, could it have been initiated from the plane’s terminal rather than the satellite network? And if so why – for example, could it be due to the plane’s terminal trying to re-establish contact with the satellite after a sharp change in direction?
As a follow-up to my post on understanding satellite pings, I thought it would be helpful to give a bit more detail on how the location of a ping can be identified. In my previous post I indicated that you could potentially measure range (based on timing) or angle (based on power). After some further thought, it is likely that the range measurement would be much more accurate, not least because a change in angle (e.g. a plane banking) would throw off the power measurement significantly. The determination of a “measurable distance” is also what David Coiley of Inmarsat described in an interview with the New York Times last week.
How does this measurement happen, and how accurate is it? The first thing to understand is that the pings are sent to the satellite in a specific “time slot”, which has a given frequency and start time, but the burst of energy in the signal might not always be exactly in the center of the slot. This is illustrated very well in a recent Inmarsat patent, which shows the variation between three different bursts B1 to B3 which are scheduled in the same frequency (f1) and successive time slots (T1-T3).
How much the burst is offset in time relative to the center of its designated timeslot gives a measurement of range, since the further the terminal is away, the longer the energy will take to reach the satellite. How much the burst is offset in frequency relative to the center of its designated timeslot gives a measurement of speed, since if the terminal is traveling towards the satellite, the frequency will get higher and if it is traveling away from the satellite, the frequency will get lower (this frequency offset is the Doppler effect).
So in the illustration above, B2 is shifted both in time (range) and frequency (speed), whereas B3 is shifted in frequency (speed) but not in time (range).
UPDATE: One complicating factor is that if the Doppler correction takes place only in the terminal itself, then it is possible that the network may not see much if any frequency shift for the ping that is returned from the terminal. I am trying to confirm how this aspect is handled.
I should also note that it would not necessarily be expected to be standard operating procedures for a satellite operator like Inmarsat to save the precise time/frequency offset associated with each burst received by its satellites. But since the precise time data appears to have been used in the range calculation, it seems logical to conclude that this information (and potentially the associated frequency offsets as well if these are available, although this was not mentioned in a CNN interview today) must have been recorded.
Key point 1: It is likely to be feasible to calculate the range and possibly also the speed relative to the satellite from the ping information via the time/frequency offset method described above.
What we’ve seen in terms of the arcs of possible locations so far just represent the range component of this measurement. It seems that there is no triangulation involved (which is consistent with the CNN interview), because in this particular coverage region the specific frequencies involved are only used on the Inmarsat 3F1 satellite and not on any other satellites.
Its much harder to interpret the speed component (if it is available), because it is the speed relative to the satellite. So if the terminal was moving along one of these arcs, it would not be getting closer to or further away from the satellite and there would be no frequency shift. So in that situation the signal would look the same as from a plane that was stationary on the ground at the time of the transmission. If this information is actually available would expect Inmarsat to have been able to interpret the frequency shift as well as the time shift, but even then there would be no easy way to illustrate “relative speed” on a chart like the one given above.
Key point 2: Speed relative to the satellite is not the same as absolute speed, so (even if this information were available) it would not be possible to determine with certainty if the plane was on the ground and stopped.
Similarly, comparable data has not been released for previous “pings” before the last one. Whether or not the frequency/speed data is available, I would expect that it should be possible to determine that some points on the arcs above are more likely than others, but even with both pieces of information it is unlikely to eliminate any points completely unless other information is known (or assumed). For example, if one assumed that the plane flew at a constant speed and bearing then it would be possible to narrow down the locations quite significantly (because the speed and range would change in a predictable way, although north/south ambiguity would remain). However, that may or may not have been the case.
UPDATE: Similarly, one could test the theory about “following another aircraft” because the track of the other aircraft is known and its position would have to coincide with the arcs calculated for intermediate pings while this “following” was in progress.
Key point 3: The combined information from multiple pings would potentially be fairly dispositive as to whether the plane flew at a constant speed and bearing (i.e. on autopilot), although there might still be some uncertainty in the ultimate location (and north/south ambiguity) unless speed information was also available. The intermediate pings would also determine whether the “following another aircraft” theory is feasible.
So now for the big question, how accurate is the location of this arc. Without the ability to triangulate between multiple satellites, then geolocation accuracy (i.e. the ability to identify where on Earth a signal is being transmitted from) is considerably reduced, but a single satellite geolocation detector from Glowlink is said to have an accuracy of 40-60 miles. However, that detector may use more measurements (of a static source) than is possible with this limited number of pings from a terminal that is moving around. So I would expect my initial estimate of say 100 miles is still fairly reasonable. Its also important to remember that the plane could have had enough fuel onboard to have flown as much as a couple of hundred miles after the last ping.
Key point 4: The range accuracy is unlikely to be much better than 100 miles, and perhaps more because the plane could have continued flying after the last ping.
UPDATE: This is the latest search area, as shown by Reuters Aerospace News, including up to 59 minutes of potential travel after the final ping (i.e. the full period before the next hourly ping, regardless of remaining fuel).
UPDATE (Mar18): The Australian Maritime Safety Authority has held a press briefing today at which they described exactly the procedure outlined above for the southern route, i.e. assuming a constant speed and heading and correlating the results from all of the pings. They have produced the following map based on NTSB analysis showing that there only two paths consistent with the set of arcs and a constant speed/heading assumption. They declined to speculate on the northern route but indicated in the press briefing that similar analysis had been conducted. Presumably therefore it is now known whether or not the “following another aircraft” theory is feasible.
UPDATE (Mar 19/20): This evening, CNN put the image below on screen, showing purported ping arcs and the overlap with one of the projected southern tracks. It is not known if these are accurate locations, or if the image was purely illustrative. However, if the arcs are accurate, then (if the debris is a false lead) the “shadowing” hypothesis can be ruled out because the plane would not have gone far enough out into the Bay of Bengal. Moreover, if the plane is found in the southern search area having traveled along one of the projected paths, then it was flying in a straight line at constant speed (as AMSA and NTSB previously assumed in making these projections) and so was not likely to have been under active pilot control when it crashed. In addition, if the plane is found in the identified search area so quickly, it will intensify the scrutiny of the delays in making use of the ping information which Inmarsat provided very early in the investigation.
UPDATE (Mar 20): As noted by a commenter, the Washington Post published 3 of the earlier ping arcs in a graphic shown below. These are quite similar to the ping arcs depicted by CNN, suggesting that if the 4.11am ping arc is as close to the 5.11am arc as suggested by the CNN graphic, the “shadowing” hypothesis for the northern route is likely to be infeasible.
There’s so much confusion about the satellite communications aspects of the MH370 incident that I thought it would be useful to give a little bit of background and an analogy to aid understanding of what we know and what we don’t. As with all analogies, this is perhaps oversimplified, but may help those without a detailed knowledge of satellite communications. I’m not a satellite designer, so I may also have overlooked some of the intricacies – please feel free to chime in with any corrections or amplifications.
Firstly, it needs to be made clear that the radar transponder “squawks” and the satellite communications “pings” are from completely separate systems (just because its talking about a transponder, that is nothing to do with satellite transponders). The radar transponder sends an amplified signal in response to reception an incoming radar transmission, which has much more power than a simple reflection from the metal skin of the plane, and has additional information about the plane’s ID. If turned off, less sensitive civilian radar will struggle to pick up the plane’s reflection, though military (air defense) radar should still be able to see the plane. But military radar systems are looking for hostile forces and have missed civilian aircraft in the past (e.g. the Mathias Rust incident).
Key point 1: The transponders are nothing to do with the satellite communications system.
So let’s turn to the satellite communications system. There has been talk about ACARS transmissions for monitoring the status of the plane. That is a communications protocol, separate from the underlying satellite (or VHF radio) link. Think of ACARS as like Twitter. I can send a message from my cellphone, which may or may not include my location. When I’m at home, on WiFi, the message goes to Twitter via my home broadband connection. Similarly, when the plane is over land, the ACARS message goes over VHF radio to SITA, who then send it on to the destination (e.g. Rolls Royce if the purpose is engine monitoring, Malaysian Airlines if its an internal airline message, or the Air Traffic Control center if its a navigation related message). [ACARS messages can also be sent over long distances via HF radio, but its not been suggested that was the case on MH370.]
With Twitter, when I leave home, my cellphone connects to the cellular network, and my Twitter messages go over that. But it makes no difference to the message and Twitter doesn’t care. Somewhat similarly, when the plane goes over the ocean, the ACARS system sends its messages over the plane’s satellite connection instead, but it doesn’t affect the content of the message.
Just like I use AT&T for my cellphone service, the plane’s satellite communication system is from Inmarsat, but so long as I have bought the right data service from AT&T, Twitter will work, and so long as I have an Inmarsat data service, ACARS will work fine.
Key point 2: ACARS is an “app” (communications protocol) which can operate over different (satellite and VHF) communications links.
I can sign out of Twitter on my cellphone and then won’t be able to transmit or receive Twitter messages. But that has nothing to do with whether my cellphone is connected to AT&T’s network. Similarly, the pilots can terminate ACARS sessions and stop reporting their position or other data (see for example this document), but that doesn’t affect whether the satellite terminal itself is connected to the Inmarsat network.
Key point 3: ACARS reporting can be disconnected without affecting the underlying satellite communications link.
On my cellphone, even if I’m not sending any data, AT&T needs to know if I’m registered on the network. When I turn on my phone, or move from cell to cell, the network exchanges data with the phone to make sure the network knows which cell the phone is located in. More importantly, even if I stay in one place with the phone in my pocket, the cellphone network checks in occasionally to make sure that the phone is still active (and say the battery hasn’t run out without the phone signing off from the network, or I haven’t gone into an underground car park and the connection has been lost), so that it knows what to do with an incoming call. You don’t normally notice that, because the timescales are pretty long (you don’t usually go into a car park for an hour or two). As another example, if I go to France with my AT&T phone, when I turn the phone on, it is registered in the Visitor Location Register (VLR), but eventually, after I stop using the phone there, my details are purged from the VLR.
Similarly with the Inmarsat connection, the network needs to know if it should continue to assign network resources to a particular terminal in case a communications link needs to be established. Not every aeronautical terminal in the world will be active simultaneously, and indeed there are quite a few that are rarely if ever used, so Inmarsat doesn’t provision resources for all terminals to be used simultaneously. However, once a given terminal are turned on, it needs to be contactable while it is inflight. So the Inmarsat network checks in with the terminal periodically (it appears to be roughly once an hour), to ensure that it should continue to be included in the list of active terminals and gets a message back to confirm that it should remain registered. These are the “satellite pings” that have shown that MH370 was still powered on and active after the ACARS messages and radar transponder were turned off, because the terminal was responding to the requests from the Inmarsat network to confirm it was still connected.
Key point 4: The “satellite pings” are due to the Inmarsat network checking that the terminal on board the aircraft is still connected to the Inmarsat satellite system and the terminal responding in the affirmative.
So now the question is how accurately does the Inmarsat network know where the plane is located? To go back to my cellphone analogy, when the network is checking my phone is still connected, it looks in the last cell it was registered. If I move to a different cell, then my phone should check in with the network to request a new assignment. But AT&T doesn’t need to know my precise position within the cell, it just needs to know where to route an incoming call. Similarly with Inmarsat, there isn’t a need to know exactly where in a cell the plane is located, just that its there and not somewhere (or nowhere) else.
Key point 5: The “satellite pings” indicate the plane is in a cell, but do not intrinsically give specific position information.
How big is a “cell” on the Inmarsat network and why the confusion? First of all, we need to recognize that there are different Inmarsat network architectures for different generations of aeronautical terminals. Think of it like 2G, 3G and 4G phones. If I have a first generation iPhone then I can only use 2G (GSM+EDGE), an iPhone 3G can use 3G, and an iPhone 5 can use LTE. AT&T supports all of these phones, but in slightly different ways. Inmarsat introduced a new SwiftBroadband aeronautical service in 2010, using its latest generation Inmarsat 4 satellites (like AT&T’s LTE network). That has much smaller spot beams (“cells”) than the older Inmarsat 3 satellites. And the Inmarsat 3 satellites (like AT&T’s 3G network) in turn have regional spot beams as well as a “global” beam (covering an entire hemisphere) to support the oldest aeronautical terminals.
As an aside, part of the SwiftBroadband communications protocol (essentially identical to BGAN) conveys (GPS-based) position information to the satellite when establishing a connection, so that the satellite can assign the terminal to the right spot beam. But it isn’t clear that GPS data is required as part of the “pings” which maintain registration on the network. That was one additional source of confusion about whether the specific position was being reported.
In any case, it appears that MH370 had a Swift64 terminal onboard (or possibly an older Aero-H or H+ terminal), not one of the latest SwiftBroadband terminals (that’s hardly surprising since SwiftBroadband is not yet fully approved for aeronautical safety services and is mostly used for passenger connectivity services at the moment, which don’t seem to have been available onboard). This is the equivalent of the iPhone 3G (or the original iPhone), not the newest version.
In the Indian Ocean, Inmarsat’s Classic Aero services, which are provided over both Swift64 and Aero-H/H+ terminals, operate on the Inmarsat 3F1 satellite located at 64E (equivalent to AT&T’s 3G network not its latest LTE network), and can use both the regional and global beams, but it appears that Inmarsat’s network only uses the global beam for the “pings” to maintain network registration. Otherwise it would have been possible to rule out a location in the Southern Ocean.
Key point 6: The “satellite pings” were exchanged with the Inmarsat 3F1 satellite at 64E longitude through the global beam.
So how can anyone find the position within this enormous global beam? There are two potential ways to measure the location:
1) Look at the time delay for transmission of the signal to the satellite. This would give you a range from the sub-satellite point if measured accurately enough, which would be a circle on the Earth’s surface.
2) Measure the power level of the signal as received at the satellite. The antennas on the satellite and the plane amplify the signal more at some elevation angles than others. If you know the transmission power accurately enough, and know how much power was received, you can estimate the angle it came from. This again would produce a similar range from the sub-satellite point, expressed as a circle on the Earth’s surface.
[UPDATE: I believe that the first of these approaches is more likely to produce an accurate estimate. See my new blog post for more information on locating satellite pings.] We can see in the chart below (taken from a Reuters Aerospace News photo of the search area posted at the media center) that the search locations are based on exactly these curves at a given distance from the sub-satellite point. However, it is unlikely that the measurements are more accurate than within say 100 miles.
We can also see that the arcs are cut off at each end. The cutoff due east of the sub-satellite point may be due to the fact that the transmissions would also potentially be received by Inmarsat’s Pacific Ocean Region satellite at that point, and if they weren’t, then that region would be ruled out (although others have suggested that military radar plots have already been checked in these regions). Its possible that the boundaries to the north and south have been established similarly by the boundaries of Inmarsat’s Atlantic Ocean Region satellite coverage, but they may instead be based on available fuel (or simply the elapsed time multiplied by the maximum speed of the plane), rather than the satellite measurements per se.
UPDATE (Mar 18): I originally attributed the picture below to a Malaysian government release, based on information from a journalist in Kuala Lumpur. As a commenter below notes, the diagram was put together based on an interpretation of what was stated in a briefing (indicating that the ends of the arcs were determined based on the minimum and maximum speed of the aircraft, rather than being based on the overlap of the Inmarsat satellite coverage areas) and is not an official document. Apologies for any confusion.
Key point 8: The position of the aircraft is being estimated based on the signal timing/power measured at the satellite. Its not based on the data content of any message and is not highly accurate.
ADDITIONAL POINT (Mar 17): Many have asked why it took so long to figure out where these satellite pings were coming from. Taking an extension of the analogy above, assume you have a friend staying in a hotel. The hotel catches fire and burns to the ground and your friend’s regular Twitter updates cease. For the first few days, the fire department is trying to find his body in the hotel. When he can’t be found the police check to see when his iPhone was last turned on. It turns out the phone was still connected to AT&T’s network hours after the fire. So then the police ask AT&T to figure out where the phone was operating by looking at their database of network records.
That’s exactly the sequence of events here. The plane’s ACARS (and radar) communications suddenly ceased and in the first few days, everyone assumed there had been a crash and was looking for the crash site. After no debris was found, investigators started to look at other possibilities. Inmarsat discovered the plane’s terminal was still connected to their network even after the ACARS messages ceased. Then it took a bit more time to calculate the location of the pings from Inmarsat’s network data records.
Finding missing people this way using cellphones is well known, but no-one’s ever had to do it before in the aeronautical satellite world, so its hardly surprising that this would be not be standard practice in an air accident investigation. I’m sure it wasn’t standard practice for cellphone companies in the 1980s either.
UPDATE (Mar20): The WSJ is reporting that Inmarsat had this information very quickly but the Malaysian government delayed making use of ping arc data to revise the search area for several days.
I hope that’s helpful. Let me know of any questions or need for further explanation.
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