Many argue the most critical payload Reaper carries is sensors for finding targets and collecting information that is made available to operators on the ground. The current version of the Reaper has a Multi-Spectral Targeting System that combines infrared and optical sensors and a laser designator/range finder to employ Hellfire missiles and laser guided bombs.
But the ability of these sensors to identify targetsto discern just what they are, based on the clarity and resolution of the imagery received on the groundhas serious limitations.
According to test reports, these sensors have had difficulty finding and tracking targets as large as vehicles, and they have even more difficulty with dismounts (people). To improve the resolution of these sensors, Reaper operates at altitudes well below its nominal 25,000 to 50,000 foot ceiling; they typically operate at 10,000 to 15,000 feet to enable better image resolution, and they may operate lower than that, if severe terrain and vulnerability to hand held air defenses is not a problem.
Some Reaper and Predator imagery has appeared on the internet. One should assume that the quality of these images is degraded by the reproduction on the internet; however, even assuming that as an analytical precaution, the quality of the imageryspecifically the ability to discern the nature of dismounts (people) and whether they are or are not legitimate targetsis very clearly very limited.
The failure to be able to discriminate valid human targets was vividly and tragically displayed in a combat engagement in April 2011 involving Marines and the Taliban in Afghanistan. A Predator was unable to discriminate the highly distinctive combat outline of two Marines (with full battle equipment) from the irregular enemy. Based simply on detecting muzzle flashes and making a poorly informed assessment based on their geographic location in the middle of a fluid firefight, a Predator with Hellfires killed two Marines, mistaking them for the enemy. As the internet video cited above makes abundantly clear, the quality of the imagery transmitted to screens on the ground from operational altitudes is so poor it cannot make critically important distinctions.
Reaper is commonly described to have a Synthetic Aperture Radar (SAR) for finding and identifying targets through weather (which the other sensors are unable to attempt). However, according to DODs Director of Operational Test and Evaluation (DOT&E), the SAR has been problematic, in part due to power and payload limitations: Reaper remains unable to execute all-weather Hunter-Killer operations. The SAR is the only MQ-9 system capable of providing MQ-9 UAS with the capability to find, fix, track, and engage targets through the weather. If the SAR were to be available, several experts cautioned the author that it remains quite controversial whether SAR imagery would materially assist the ability to actually find and identify targets.
According to GAO, Reapers Block 5 upgrade will attempt to address these and other deficiencies, by attempting to remediate poor performance in area surveillance and the ability to detect dismounted soldiers. These improvements are not expected to be available until 2014 to 2015. The extent to which they will be effective is unknown, but it is notable that problems in Predators (and by implication Reapers) sensors have been an issue for a long time. A report as early as 2001 from DOT&E noted them;  the problems are persistent, and assuming a new technological development will eliminate them has proven to be a false hope in the past.
Reapers sensors and endurance might seem tailor made for the task of border surveillance and assisting the apprehension of illegal aliens and drug smugglers crossing the border. The terrain in the US southwest would seem near-ideal for such operationsbeing relatively flat, barren and arid, especially compared to the extremely rugged terrain in much of Afghanistan. And, there is no air defense to worry about or to limit low altitude searching. Thus, one would expect Reaper and other drones to excel. Indeed, drones were declared a force multiplier by Customs and Border Enforcement in the Department of Homeland Security (DHS).
Customs and Border Protection (CBP) in DHS has been attempting to employ drones for border surveillance for several years. The simpler and cheaper Hermes and Hunter drones were initially employed, and the experiment was assessed in a December 2005 report from DHSs Office of Inspections and Special Reviews. The report found that those drones cost $1,351 and $923 per hour to operate (considerably less than Predator), but those costs were double the cost of manned aircraft to operate. More importantly, those drones were found to be significantly less effective than manned aircraft in finding and helping to seize immigrants or marijuana crossing the border illegally. The report also found that when the drones did play a role in seizures, the role was secondary in that they simply assisted in the seizure of illegals already detected by other means. The drones sensors were impeded by weather in the mild form of clouds and humidity, and finally the drones high accident rate impeded operations.
CBP subsequently purchased six Reapers (reported as Predator Bs) for southwest border enforcement. As of June, 2011, they had flown 10,000 hours, which led to the apprehension of 4,865 undocumented aliens and 238 drug smugglers. This was 1.5 percent of the total reported number of 327,577 illegal immigrants caught in the same time frame, and based on an operating cost estimate of $3,600 per hour, Reapers cost-effectiveness calculated to $7,054 for each illegal immigrant or drug smuggler caught.
In assessing these Reaper operations, GAO also considered a program dubbed Big Miguel that consisted of a manned Cessna aircraft with a forward looking infrared (FLIR) sensor acquired and operated for $1.2 million for a yeari.e. one quarter the cost of acquiring one Reaper air vehicle without its support infrastructure and without the cost of operations. According to GAO, the Cessna/FLIR program found and assisted in the apprehension of 6,500 to 8,000 undocumented aliens and the seizure of $54 million in marijuana. Those numbers calculate to a cost per illegal alien for the Cessna at $230 per alien, or 3 percent of the Reapers per alien cost.
The manned Cessna was far cheaper to both buy and operate than the Reapers bought by CBP, and the Cessna was more effective. The experience was summed up by an official of the Border Patrol Union: Unmanned aircraft...are not economical or efficient in civilian law enforcement applications...there are a number of other [manned] technologies that are capable of providing a greater level of usefulness at far lower cost. It appears that the contractors have once again managed to sell a bill of goods to the politicians and bureaucrats who oversee the procurement of technology designed to secure our borders.
These awkwardly costly and ineffective results notwithstanding, Congress has called for still more domestic drone use. In February 2012, a new authorization statute for the Federal Aviation Administration called for a comprehensive plan to safely accelerate the integration of civil unmanned aircraft systems into the national airspace system...as soon as practicable, but not later than September 30, 2015.
Next: How Many Drones Are There? How Many Have Crashed?
 See a longer discussion of these limitations in an analysis of the Gorgon Stare equipment that has been added to some Reapers; find it at Gorgon State Is Not Operationally Effective and Not Operationally Suitable, Winslow T. Wheeler, January 27, 2011 at http://www.cdi.org/friendlyversion/printversion.cfm?documentID=4637.
 Find samples of these videos at http://www.youtube.com/watch?v=GShSMMLooJg&feature=related, http://www.dvidshub.net/video/133189/last-convoy-out-iraq, and http://www.youtube.com/watch?v=Smh-HwtDHI8&feature=related.
 See MQ-9 to Provide Full HD Video by 2015 after Two-phased MTS Upgrade, Inside the Air Force, 1/20/12, Gabe Starosta.
 Pp. 21 ff, Operational Test & Evaluation Report on the Predator Medium-Altitude Endurance Unmanned Aerial Vehicle (UAV), September 2001, Director of Operational Test and Evaluation, Department of Defense.
 P. 10, Fallacies of High-Tech Fixes for Border Security, Tom Barry, International Security Report, Center for International Security, April 2010, at http://www.ciponline.org/images/uploads/1004_TBP.pdf.
 P. 16, A Review of Remote Surveillance Technology Along US Land Borders, Department of Homeland Security, Office of Inspector General, Office of Inspections and Special Reviews, OIG-06-15, December 20005, at http://www.oig.dhs.gov/assets/Mgmt/OIG_06-15_Dec05.pdf.
 P. 10, Fallacies of High-Tech Fixes for Border Security, Tom Barry, at http://www.ciponline.org/images/uploads/1004_TBP.pdf.
 P. 4, Homeland Security: Unmanned Aerial Vehicles and Border Surveillance, Chad C. Haddal, Jeremiah Gertler, Congressional Research Service, July 8,2010, RS21698, at http://www.fas.org/sgp/crs/homesec/RS21698.pdf.
 See More Predator Drones Fly US-Mexico Border, William Booth, Washington Post, December 21, 2011, at http://www.washingtonpost.com/world/more-predator-drones-fly-us-mexico-border/2011/12/01/gIQANSZz8O_story.html.
 P. 32, Observations on the Costs and Benefits of an Increased Department of Defense Role in Helping to Secure the Southwest Land Border, Government Accountability Office, September 12, 2011, GAO-11-856R, at http://www.gao.gov/assets/100/97733.pdf.
 More Predator Drones Fly US-Mexico Border, William Booth, at http://www.washingtonpost.com/world/more-predator-drones-fly-us-mexico-border/2011/12/01/gIQANSZz8O_story.html