Open Skies

Kevin Wright reports on the Open Skies Treaty and the aircraft and equipment used to implement it.

THE OPEN SKIES treaty was signed in March 1992, representing, in diplomatic terms, the culmination of a very rapid and intense period of negotiation, between 1990 and 1992. The result was a highly complex technical agreement, aimed at allowing participating states to overfly each other’s territory to monitor their military establishments and activities — a regional confidence and security building measure.

The original idea of an Open Skies regime was first presented by President Eisenhower in July 1955 to a four-power conference in Geneva, during which he proposed a mutual overflight regime between the USA and the USSR. Although a bold political move on the part of Eisenhower, the concept was rejected by Khrushchev almost immediately after the meeting — he saw it as little more than a bold espionage plot against the Soviet Union. The idea remained dormant until 1989 when President Bush called for a revival of Eisenhower’s original Open Skies idea. Two negotiating rounds in Ottawa and Budapest in 1990 made slow progress, producing only joint communiques that reflected a willingness to negotiate, but little else.

Negotiations were eventually concluded on March 24, 1992 when 25 states signed the treaty. However, a number of issues relating to costs and sensors were not fully agreed and were handed over to the Open Skies Consultative Commission (OSCC) to resolve.

Sensors and Aircraft

The treaty is very specific on the categories of sensors that can be used and the limits of their performance for Open Skies flights. All of this equipment must be commercially available to signatories and falls into four categories:

1. Optical panoramic and framing cameras.

2. Video cameras with real time display.

3. Infra-red (IR) line-scanning devices.

4. Sideways looking synthetic aperture radar (SLAR).

The optical and video cameras specified are designed to take straightforward optical images and are mounted so that they can take photographs both underneath and to each side of the aircraft to a range of 31 miles (50km), up to a resolution of 113Ains (30cms). The infra-red line scanners are used to detect heat images left by people and equipment. Obviously such devices can be used at night and can penetrate cloud, as does the SLAR. This system works on the principle of being able to optically display the radar reflection from a beam directed at the ground. Such systems are very good at detecting sharp angular surfaces, such as buildings and vehicles etc. Resolution of these devices must not be greater than 16ft (5m), and the range no more than 15 miles (25km).

The sensors are mounted in two different ways. They can be mounted within the aircraft — this method has been undertaken by the United States using modified WC-135s; the United Kingdom using Andovers, at least until 1995; and Germany has proposed to use it with its Tu-154s. The US has chosen to mount two Chicago Aerial KS-87B oblique view cameras and another for centre-line use, as well as a KA-91A for higher altitude use, with the remaining systems to be added later.

The alternative is to carry all the sensors in an external pod. Lockheed has developed such a device for use on C-130s named SAMSON (Special Avionics Missions Strop-On Now), mounted in an external fuel tank position and with a palletised operators’ console that can be inserted and removed as required. The pod utilises a Litton ITEK PC-15 panoramic camera as its primary sensor, but also incorporates a Texas Instruments AM/AAS 36 (LW) FUR, which is currently not permitted under the treaty. The system was tested on a Belgian C-130 on April 7,1992, during a trial flight over Poland. The biggest advantage of the second option is that it appears to be a very economical solution and offers possibilities for joint procurement and/or use, which may well make it of greater interest to the smaller states.

In addition to sensor certification, the various types of aircraft to be used for Open Skies missions have also to be certified. This involves providing considerable information concerning the aircraft’s dimensions, equipment, ground handling, communications fits, etc, to all the other participating states.

Organisational and institutional aspects

The basis of the treaty is an inter-governmental one, but with important provisions for states to combine their efforts to form ‘Groups of States Parties’ for treaty implementation. Belgium, the Netherlands and Luxembourg, as well as Russia and Belarus, have combined to form two such groups. These combinations offer considerable scope for cost sharing by pooling aircraft, sensors, personnel, processing and interpretation costs, etc. Western European Union (WEU) members have also indicated their desire to co-operate under the Group of States Parties arrangements. However, more ambitious plans to establish a joint WEU programme have had to be abandoned in favour of arrangements to establish a common pool of nationally-operated aircraft. The Russian Federation has also expressed an interest in close co-operation with the WEU, but considerable difficulties still have to be resolved.

Parties to the agreement are allocated flight quotas as an ‘observing party’, known as the ‘active quota’, and a quota of flights which they must be prepared to receive as the ‘observed party’, the ‘passive quota’. These quotas are established by negotiation within the OSCC, and the provisional allocations are shown in Table 1. This table also shows each year’s allocation of flights for the first three years of the treaty’s full operation. Until the treaty is ratified by 20 of the signatory states an interim period of operation applies where only the most simple of the sensors can be used and the SLAR and IR line-scanning devices are prohibited. The number of overflights is to be fixed a year in advance and the scheduling for the quarter must be agreed at least six weeks in advance, while individual flights require at least 72 hours notice of arrival and must generally be completed within four days of arrival.

Flights can only enter, depart, and conduct missions from specified airfields within each state, and a list of these is provided within Table 2. Flights are restricted to the maximum overflight distance that can be flown on a single monitoring mission — air-to-air refuelling is not permitted for monitoring flights. Flights arriving and departing airfields before and after monitoring missions must have the sensors covered and/or locked and these are to be inspected by the observed nation. Individual flight plans have to conform to normal International Civil Aviation Organisation (ICAO) standards taking into account any hazardous airspace etc. Essentially, they fly in straight lines between targets in a set sequence that does not permit circling or sudden deviations, and they must not fly within six miles (10km) of a non-signatory state’s borders.

Costs of collection and analysis

Collection of data under the provisions of Open Skies will be relatively expensive. Early figures suggest that significant costs are being incurred by the need to modify existing aircraft with the permitted sensors. Estimates from the USA reckon that conversion of each C-135 will cost $18-20 million, with the cost of each monitoring flight estimated to be in the 5200,000 bracket. German defence budgets have allowed sums totalling DM111 million between 1993-96 to cover costs involved in treaty implementation.

Once data has been collected by the overflight, provisions are made within the treaty to allow all signatory states to have copies for analysis if they require. Specialist data analysis tends to be readily available only to the larger military powers in Europe and the United States. Without the capability to expertly analyse the value of the data gathered from Open Skies, monitoring flights will be significantly degraded. It is therefore possible that those states most likely to benefit politically from the data, namely the smaller ones of central and Eastern Europe, will be the most disadvantaged.

An obvious way to disperse and reduce these costs is to share data collection and analysis. Such considerations appear to have been instrumental in persuading the WEU to combine to form the Group of State Parties. The WEU Satellite Centre at Torrejon has also been cited as a means by which data gathered under the Open Skies treaty could be jointly analysed and distributed to national capitals. However, progress towards getting this programme operational is proving very slow. Other options open to states include the chartering of observation aircraft from another state party or using satellite data.

Objectives, costs, and benefits

If financial cost is to be an important element in judging the necessity for a monitoring flight, it must be measured against the perceived benefits. These derive from the objectives of what can best be described as ‘operational arms control’, where the aim is to clarify the nature and purpose of military action, but more particularly, to reduce the possibilities of misinterpreting military activities and preventing surprise attack. However the notice time required for an Open Skies flight would also permit a fair amount of hardware dispersal to take place, and as a measure used in isolation could literally allow a ‘false sense of security’ to arise.

As well as military uses, environmental monitoring is permitted under the treaty if agreement can be reached within the OSCC. In 1992 a specialist seminar considered ways in which Open Skies could be used to contribute to ozone and global warming monitoring, deforestation measurement, water and air pollution. This requires a considerable amount of additional technology and effort which is still under discussion.

Open Skies as an adjunct to CFE

Open Skies is also seen as an adjunct to the CFE Treaty because it has the potential to provide an airborne verification element that was not included in the original treaty. Development of a full aerial verification element for CFE, once negotiated, is unlikely to come into effect until about 1996/7, an omission that Open Skies does not fully compensate for.

It is the ability for aerial monitoring to rapidly provide another angle from which to record activities over a large area, that really sets it apart from other ground and helicopter-based monitoring and verification measures under the CFE’s On Site Inspection (OSI) regime. However, the current technical sensor limitations will not always be sufficient to distinguish between items of Treaty Limited Equipment ( TLE) and non-TLE or decoys. Open Skies can perhaps best be utilised as a complementary measure. By supplementing OSIs it can help to deter cheating on the CFE Treaty by making it more difficult to escape discovery because the massive financial and resource expenditure required would be prohibitive.

Experience so far

Although not fully operative, a number of overflights have already taken place, mainly to test equipment and refine procedures. In fact a pre-treaty flight between Canada and Hungary, the treaty’s two depositories, took place over Hungary as early as January 1990. On April 7, 1992, a Belgian Air Force C-130 flew from Poznan in Poland at between 2,000ft and 5,000ft (610m and 1,524m) over two Polish Air Force bases, an army training ground, a chemical plant, and three Russian facilities. It used a panoramic camera and FUR, which is not yet permitted under the treaty but did help to perfect procedures. The following day, a reciprocal flight was made by the same aircraft over the Benelux countries on behalf of Poland.

In September 1992 a RAF Andover undertook a number of monitoring flights over Russian territory, involving some ten hours flying time. In October 1992 Danish, Russian, and Canadian aircraft flew over special targets in Hungary to demonstrate the calibration of three different SLAR systems. Between June 16 and 19,1993, a Russian An-30 aircraft made a trial flight over the United Kingdom. The flight, conducted by 18 Russian and two Belarus personnel, covered a large number of ‘targets’, including the RAF facilities at Boulmer, Spadeadam, Leeming, Fylingdales, and Machrihanish, as well as the Sellafield and Torness nuclear plants and Clyde and Rosyth naval bases. In July the US and Hungary conducted a trial flight over CFE sites within the latter’s territory, but a major element of this trial was testing out the many and often complicated pre-monitoring flight inspection and test procedures.


In some respects just the act of flights over neighbouring territories and the wide availability of images from those flights represents a great symbolic advance in co-operation. However now that the fears of a NATO/WarPac conflict has disappeared, it will be the degree to which interstate suspicion persists that will determine the continuing need for such a measure.

What emerges from this technically very complex treaty is a regime that is going to operate largely at two levels. For one level, comprising states such as the US, other NATO members and Russia, Open Skies is likely to represent only a minor or modest addition to their capabilities. The pooling of data collection and analysis will help reduce overall costs of the treaty to them too.

The second group is composed mainly of Central and Eastern European states, who have no such surveillance capabilities themselves but who could gain the most politically from the treaty’s Continental Strategic Ballistic Missile (CSBM) function. For most of these states, collecting that data will represent a significant departure from previous practise, is likely to be financially expensive, and will require access to new technology to analyse and interpret that information. Meeting these needs might impose significant new burdens on defence budgets; which in some cases are already trying to cope with major reorganisation of effort.

The final issue concerns treaty coverage. Admittedly Open Skies covers the largest and militarily most heavily-equipped states of Europe, however, it is primarily those states outside the treaty that are the most likely to be in dispute with other states. While the characteristics of Open Skies and the limitations imposed upon sensors may have been suitable to cope with the detection of a large military threat within the bloc context, the ability to operate within new definitions of security could be called into question. Military action could be just one constituent threat, and could be of a scale and nature that make it less obvious to detect in the future.

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