Faced with a bandwidth crunch prompted in part by multiplying flocks of unmanned
aerial vehicles that are transmitting multi-megabyte pictures, Defense Department
planners are counting on a new generation of communications satellites to expand
capacity.
A constellation of six transformational satellite or TSAT spacecraft, comprising
five satellites and one in-orbit spare, currently are slated for launch around
2011, according to Christine Anderson, systems program director for the MILSATCOM
joint project office in Los Angeles.
Lockheed Martin and Boeing won $472 million in risk reduction contracts. In
2006, the Air Force will select a single prime contractor to build the satellites.
For the ground-based segment of the system, $3 million research contracts were
awarded to Lockheed Martin, Raytheon and Northrop Grumman. This contact will
be awarded in 2005.
If the laser-equipped TSATs are launched, they will combine the best features
of the menagerie of radio frequency (RF) communications satellites in orbit
or scheduled for launch.
Communications satellites come in three flavors: narrowband systems that are
useful for voice transmissions but lack sufficient capacity for large data streams,
wideband systems for sending large amounts of data, and protected satellites
that are hardened against jamming and nuclear effects. By way of comparison,
the current ultra high frequency follow on (UFO) narrowband satellites transmit
at a rate of two to five megabits a second.
UFO’s successor, MUOS (mobile user objective system), scheduled for launch
in 2009, transmits at 40 megabits a second. TSAT will have 25 to 45 megabytes-per-second
RF links to users on the ground, plus 20-gigabyte laser communications connecting
the satellites to each other. Thus, they will combine the bandwidth of wideband
systems such as the Wideband Gapfiller satellite, with the protected links of
spacecraft, such as the advanced extremely high frequency (AEHF) satellites.
A 24-megabyte visual image transmitted by a reconnaissance aircraft, for example,
would require two minutes to be transmitted to a current Milstar 2 satellite.
A TSAT would cut transmission time to less than one second.
Particularly cutting-edge are the laser optics that will connect the geosynchronous
TSAT satellites into an integrated network. If a signal is transmitted to a
TSAT that is not within line-of-sight of the recipient, it forwards the message
through a laser connection to another TSAT that has line of sight.
Many current satellites are not interconnected, which means that if a satellite
is not within line of sight of the destination, it must send the message back
to a teleport on the ground to be relayed to another satellite in the constellation.
While the AEHF constellation will be interconnected, it only uses slower RF
links rather than lasers.
“Transformation communications is different than other satellites we’ve
built in the past,” Anderson said. “Think of it as laying fiber
in space. What we’re doing is laying fiber via the crosslinks between
the satellites. And this provides a tremendous amount of connectivity we’ve
never had before. Instead of going with a circuit to circuit system like we’ve
done in the past with MUOS and Milstar, we’re now going to an Internet
protocol-based system that has all sorts of wonderful benefits to the user,
such as communications while on the move. We can deliver T-1 class [1.5 megabits
per second] communications to a vehicle.”
This high-speed capability has limitations. For one, TSAT requires users on
the ground to have dish antennas, which rules out foot soldiers, though not
vehicles as small as a Humvee. Anderson said studies are underway to examine
the feasibility of the new joint tactical radio system to communicate with TSAT.
Another problem is that TSAT’s high-powered lasers suffer from weather,
forcing it to use RF communications with the ground while reserving its lasers
for receivers in space and in high-flying aircraft. “Laser communications
has the advantage of extremely high bandwidth, orders of magnitude higher than
RF,” said Anderson. “But it cannot penetrate through cloud cover.
You basically use it for cross-connecting in space, and also to link manned
and unmanned aircraft.”
Most damaging is a General Accounting Office report published last December
that recommended that TSAT be delayed until its critical technologies, such
as laser optics, high-speed router and security algorithms, are more mature.
Most of these technologies are at technology readiness level (TRL) 3 or 4, according
to GAO.
“When a technology is classified as a TRL 3, it means most of the work
performed so far has been based on analytical studies and a few laboratory tests
may have been conducted,” the study said. GAO also pointed to a lack of
backup technologies for critical systems such as laser communications.
Anderson, however, countered that GAO had based its report on a previous launch
date of 2009 rather than the current 2012 time frame, and that the TSAT technologies
have further matured. Joe Davidson, spokesman for the Air Force’s Space
and Missile Systems Command, said the risk reduction contracts awarded in January
are intended to bring TSAT technologies to a mature TRL 6 level.
“Current experiments have already demonstrated the successful use of
laser communications in space,” Davidson said. Should the laser optics
not work as advertised, TSAT satellites could be limited to transmitting at
lower data rates, or designed with shorter life spans using more traditional
technologies. For example, if TSAT’s dynamic bandwidth resource allocation
system, which boosts transmission power as needed, isn’t mature in time,
then the satellites could use fixed power allocation, according to Davidson.
By next November, the Defense Department must decide whether to go ahead with
TSAT, or instead add two more AEHF satellites to the three AEHF craft slated
for launch beginning in 2007.
TSAT’s fiscal year 2004 budget has been cut by $100 million, which caused
a nine-month delay.
The estimated system cost for TSAT through 2016 is $18 billion, which includes
the satellite, the ground operations system, the satellite operations center
and the cost of operations and maintenance.
TSAT proponents say that transforming satellite communications is key to military
transformation. “TSAT is part of the vision to enable the overall packet-based
transformations being instituted by the office of the secretary of defense and
the services’ next generation concepts,” said Davidson. “You’re
not just providing users with a phone line, like the telephone company,”
Anderson said. “You’re connecting them to the global information
grid. If someone is moving through the desert, and they want to search all intelligence
imagery of the area, they can do that.”
Rear Adm. Rand Fisher, director of naval space technology programs and head
of the Transformational Communications Office within NRO, oversees the transformational
communications architecture (TCA), an ambitious effort to link three families
of next-generation communications satellites.
The TSAT program is critical to this architecture, he said. While the Defense
Department manages the TSAT, the intelligence community is working on the optical
relay communications architecture. NASA manages the tracking and data relay
satellite system (TDRSS-C).
“TCA introduces optical communications, which is far higher bandwidth
than radio frequency communications,” Fisher said. “It will also
introduce ‘packetized’ information transport in an Internet protocol
environment.”
“Imagine yourself with just a phone with just audio information,”
Fisher said. “Now contrast that with voice and video data in a collaborative
environment where you are sharing real-time information around the world and
across defense, intelligence community and NASA boundaries.
“We know we have gotten information to commanders too late,” said
Fisher. “We find there was a lot of information available that we couldn’t
get to the right people at the right time. I hesitate to use the word ‘crisis,’
but I know at least some of our war fighters have at times thought of it as
a crisis.”
Fisher termed the GAO report “very pessimistic,” adding that there
is always risk inherent in new technologies, but sticking to only mature technologies
will stifle innovation.
Fisher said there are two problems that concern him. First is the question
of if and when TSAT will be deployed, especially in light of the GAO report.
By next December, the Defense Department must decide whether to proceed with
TSAT, or substitute additional advanced extremely high frequency system (AEHF)
satellites.
Successors to the current Milstar system, three AEHF spacecraft are scheduled
to be launched around 2007. But two more could be launched in place of TSAT.
While AEHF has just one-twentieth the bandwidth capacity of TSAT, it has the
advantage of using proven radio frequency communications rather than cutting-edge
laser communications.
“If you believe that there is inherently too much risk in the program
to not build an AEHF, then the question becomes, ‘do I take that money
for the AEHF out of the TSAT side?’” Fisher asked.
“If we end up taking money from the TSAT line, we end up delaying TSAT,
and then because we end up delaying TSAT, then we need to launch another AEHF.
If you keep taking money from the TSAT program, I’m not sure how you get
anywhere. Every time you build an old satellite, you propagate the old architecture.
That’s the dilemma that we have.”
Complicating the picture even further is the fact TCA functions at its best
as an integrated triad. Though the military, intelligence, and NASA satellite
constellations operate independently, they are designed to be compatible. Because
each of the three communities is responsible for securing the funding for its
own satellites, Fisher is concerned that the three programs won’t be funded
synchronously.
“It’s both a community and a congressional issue,” he added.
“We are a large team in that regard. And when you have a large team, you
can expect some natural stress or conflict and that all the team members don’t
gauge the priorities in precisely the same fashion.”
Fisher, nonetheless, contends that launching the TSAT around 2011 is key. “Everyone
we’ve chatted with, including people on Capitol Hill, really sees the
need for the capability that the TCA brings. All of the services are making
plans that are dependent on those capabilities. The desired position we would
like to be in is to have enough confidence in the TSAT Version One that we would
not have to buy AEHF 4 or 5.”