As I stated in the introduction to my last post (see below), the most common wilderness-capable emergency signaling devices are Personal Locator Beacons (PLBs), Satellite phones, and SPOT satellite text messengers. The last post covered PLBs. This time we examine satellite phones. And to recap, I feel that each is a trade-off between signal reliability versus rich communications, and each is perhaps ‘best’ for a different user. Below I’ll discuss how sat phones work, the systems available, their benefits and drawbacks. Because of the details, it’s longer than my usual post.
For sheer reliability of getting a “help me now” dire emergency signal out, world-wide, your best choice is a PLB. On the other end of the spectrum lie satellite phones, which are more expensive and fragile, with a less reliable signal than beacon-style devices, but offer far better communications. In addition to helping with logistics, that can have important implications in medical situations.
Unlike PLB’s, which are tough to actually ‘test’, I’ve used satellite phones quite a bit from northern Alaska to the continental U.S., and I find them super-useful, subject to a modest learning curve. In a nutshell, the satellite phone models appropriate for backcountry use weigh about a pound, are the size of a spray can, and usually come with an array of wall and car chargers for their replaceable, rechargeable lithium-ion batteries. For field security, you should carry them with a spare battery, in a Ziploc, inside a padded case. Liter-bottle cozies usually fit well.
To the user, sat phones work a lot like a cell phone. You unfold the antenna (it should always point vertically), then power up and wait for bars to show satellite contact. Unlike cell phones, the most common satellite phones in North America (Globalstar and Iridium), have robust batteries that hold a charge for weeks and run a lot of talk time. I’ve made twice-daily 5-minute dispatches for 11 days straight on a single sat phone battery. Once you’re connected, you punch in long distance numbers like any call. For land-liners making calls to sat phones, Globalstar and Iridium networks have their own country codes.
And just like a cell phone, you don’t always get bars. Satellite phones do not work well underneath tree cover, inside tents, or in moving vehicles. High surrounding horizons like peaks and canyon rims drastically reduce your talk time window as satellites pass overhead. Unlike cell phones, with a satellite phone you find the most open position to make your call, then power up and wait for a satellite to crest the horizon. If you’re waiting for bars to come up, or your call gets cut off as a satellite sets, you may have to wait 20 minutes before the signal comes back. Moving around and waving your phone, ala cell use, does no good. Similarly, you shouldn’t pace back and forth while making a sat phone call.
These very noticeable drawbacks are usually more annoying than dangerous, except in the most frantic of emergencies like boat sinkings. The long evacuation times normal in wilderness emergencies often negate the half hour time lag in EMS notification. However, there are many locations where a sat phone signal might be impossible.
With a little flexibility in transmit location, satellite phones offer two-way voice and data communications, which makes them very useful for large groups and wilderness outfitters. In fact, I recommend every university outing group, club or scout troop carry a rental satellite phone on committing trips (and know how to use it).
The reasons are simple: a large group can usually spare someone to move to a better signal location. Also, the larger the group, the more certain it is that someone will have existing medical conditions like allergies, or epilepsy, or bipolar disorder, or some internal medicine problem. In remote situations, diagnosing and stabilizing these patients might require phone consultations with a doctor. Simpler emergencies, a troublesome client, or even a death in someone’s family might dictate a rendezvous with people who’ll evacuate the patient/victim/assailant, while the rest of the group continues. Or perhaps the emergency is simply that you’re running out of food, and require resupply (beer too) from your buddy with the Jeep. Satellite phones are the only device that can handle these needs.
Most sat phones need line-of-sight clearance to communicate with their “constellation” of satellites. They work off two basic styles of satellite; low earth orbital satellites, or geosynchronous satellites.
Geosynchronous (GEO) satellites tend to be large, heavy, and expensive to launch. Their 22,000-mile-plus orbit altitudes and ‘stationary’ positions above land points mean they’re less prone to signal blockage by low ridges, or call cut-outs due to moving satellites dropping below the horizon, but there is a notable delay in conversations. However, if you can’t get a signal, you’ve got to move to a different location (rather than simply waiting) for line-of-sight connection. Then you get near-continuous coverage with no talk-time windows. Two major systems, Inmarsat and Thuraya work off geosynchronous satellites. Neither system is appropriate for normal backcountry use in North America.
Inmarsatphones are expensive ($2,000 to $5,000) laptop- to suitcase-sized units that are generally unsuitable for muscle-powered expeditions. As Broadband Global Area Network (B-GAN )terminals they have fast data transmission speeds (up to 492kb/s for downloads; 300-400kb/s for uploads). A B-GAN antenna works like a satellite TV dish; it requires precise aiming for the best signal, but the process is quick for experienced users. B-GAN terminals can be connected to both computers or normal phones. For those reasons Inmarsat phones are commonly used by industrial and scientific expeditions, in addition to ocean-going vessels. Lighter weight rental B-GAN systems have recently become available, and may be the ticket for science-oriented wilderness groups. Rates typically run about $120/week - $450/month, plus airtime of $8/MB/$1.75 minute voice.
Thuraya satphones are compact handheld phones with excellent (non B-GAN) upload speeds for transmitting photos and such. However, the single Thuraya GEO satellite only covers Europe, western Asia and northern Africa. Thuraya phones are the standard for Himalayan expeditions but do not work in North America.
The two main hand-held satellite phones suitable to North American use – Globalstar and Iridium - work off low-earth-orbital (LEO) satellite networks. These smaller, cheaper satellites move across the sky at altitudes of 400 to 700 miles, requiring a high-speed 70- to 100-minute orbit times in order to counteract the effects of near-earth gravity. Both Globalstar and Iridium have data rates fast enough for voice communication and text e-mail, but too slow for efficient photo or video upload, even at very low resolutions.
Globalstaruses a current network of 40 active satellites, orbiting at elevations around 870 miles, with an orbital inclination (angle relative to the equator) of 52 degrees. Near-polar areas are not covered. The relatively high orbit elevation means each Globalstar satellite covers a decent footprint of ground, yet conversation lag-time is still minimal. Globalstar satellites do not communicate with each other, they merely relay satphone signals to and from ground ‘gateway stations’ to the public phone network. For the wilderness user, this means that the Globalstar satellite must not only have a clear view of your satphone, it must have line-of-sight to a gateway station. In certain remote areas, or mid-ocean, there is no Globalstar connectivity even though satellites pass overhead. Despite these drawbacks, this system architecture makes for lower costs than Iridium.
In recent years, Globalstar has been plagued by reports of diminishing connectivity and dropped calls. Although I experienced few problems using Globalstar for a month in the Sierra Nevada during the autumn of 2006, by 2007 many users were reporting 1- to 2-minute talk windows even in good conditions. This is due to several reasons.
The original 52-satellite system, which began launching in 1998 from Russia’s Baikonur spaceport, was originally envisioned to work off 48 satellites and eight spares. The first 12 satellites were all lost to a launch accident. Globalstar finally launched the full constellation and four spares. Since the predicted working life of each satellite was 7.5 years, they’ve already begun decommissioning some satellites, and are in the continual process of launching new ones. That is part of the problem.
A larger factor, however, involves the satellite’s “S-band amplifiers,” which allow two-way communications by boosting the 2- to 4GHz S-band signals these phones work on. These amplifiers are failing sooner than originally expected. The problem does not affect one-way data services (such as the SPOT emergency beacons which also work off Globalstar’s system). Globalstar is already launching a new array of satellites with a 15-year life. The situation is being corrected, but at this time we don’t recommend Globalstar phones for dire emergency use unless you’ve rented and tested the system for your needs. You can rent Globalstar satphones for as little as $20/week with limited free air time.
By default, Iridium satphones should probably be considered the current choice for wilderness travelers in North America. They work off a constellation of 66 LEO satellites orbiting 485 miles high on near-polar orbital inclinations (angle relative to the equator) of 86.4 degrees. The satellites are “partially cross-linked” and thus don’t always communicate via ground-based gateways. Each Iridium satellite covers less area than a Globalstar satellite, but the denser network serves the entire globe, poles and oceans included (with varying talk-time windows). Communications reliability is excellent, although voice conversations display a lag time, and your voice often sounds like Cher’s last video thanks to strong digital compression. Iridium’s satellite constellation is expected to be workable through 2014.
One of the most useful features of Iridium is its limited text-messaging capability. Users can log onto the company’s website, enter the satphone number they wish to contact, and leave a free, short (18-character) text message that will appear on the satphone LCD the next time it’s powered up. Text messages from sat phone to landline are $0.58 each. Most Iridium phones also have data capability, but slow through-put rates make the network almost useless for photo or video uploads, even at the lowest resolutions.
As with most wireless telecommunications, the prices on satellite phones and calling plans vary widely. For most users, we strongly recommend renting and test-driving any satellite phone system you consider prior to purchasing. Rental satellite phonesare widely available at rates around $20-$40/week, $160/month, plus airtime ($0.50-$1.80/minute depending on call volume)
Next dispatch: SPOT satellite text messengers.--Steve Howe