Open Skies review

Representatives of the 34 states parties to the Treaty on Open Skies met in Vienna 7-9 June 2010 for the second five yearly Review Conference. At the opening of the meeting, which was chaired by the United States, Secretary of State Hillary Clinton expressed strong support for the Treaty in a video address ( The contrast to the May 2010 NPT Review Conference was striking since there were no controversies which might have questioned the regime itself. The focus was rather on past and future implementation. Here the main challenges are the replacement of ageing aircraft and the transition from using film-based to digital aerial cameras. This transition is overdue and market driven, since some major companies have begun to terminate production of some aerial films, as well as the chemicals used for developing them.

Going digital
Over the last five years, the Informal Working Group on Sensors (IWGS) of the Open Skies Consultative Commission has developed detailed procedures for certifying digital aerial cameras and thermal infrared imagers with digital readout. The conference’s Final Document—which was adopted unanimously—emphasized the need for this transition, which, however, is confronted with budgetary constraints in many countries (see The difficulty of funding this modernization is indicative of the political status of the treaty in many of its member states. While the treaty was initially promoted by heads of government, high level support—crucial for committing additional funding—is now dwindling in many countries. Open Skies implementation is executed by the (often small) arms control verification units of the respective defense ministries. In times of tight budgets, arms control and military confidence building often struggle to be seen as priority areas in the defense establishments’ security considerations and plans. Nevertheless, the transition to digital sensors will go ahead. Norway, for instance, intends to equip its newly assigned Open Skies aircraft, a P3 Orion, with digital sensors by 2011/12. Russia has firm plans to go digital. Meanwhile, states like the US, Sweden, Turkey and a group of nine other states (from Western and Southern Europe, and Canada), which use a common sensor pod, are studying the technical and budgetary feasibility.

Three types of digital sensors are envisaged:

  • Digital aerial cameras in the wavelength range from 0,3 to 1,1 micrometers (optical and near infra-red) at a ground resolution (ground sampled distance GSD) of 30 cm (these cameras are referred to as digital video sensors in treaty language);
  • Thermal infrared imaging sensors in the wavelength range from 7 to 15 micrometers at a ground resolution (GSD) of 50 cm;
  • Imaging radar, Synthetic Aperture Radar (SAR), at a ground resolution of 300 cm. (For a detailed explanation of Thermal and SAR sensors in the context of Open Skies see VERTIC Brief No.8, by Hartwig Spitzer, 2009)

Just a few weeks before the conference, the Open Skies Consultative Commission adopted a decision (OSCC/DEC/6/10) on the specifications and certification procedures for digital aerial cameras drawn up by the IWGS. The decision allows for cameras with up to four spectral channels (blue, green, red, near infra-red) as well as panchromatic capabilities. Such cameras offer enhanced capabilities for recognizing military objects, infrastructure and camouflage when compared to the black-and white film cameras currently used. The new sensors could also support the study of land use, vegetation, and water pollution in order to monitor effects of military activities or for purposes of general transparency. On the insistence of the Russian Federation, the decision also contains certain provisions to impede hyperspectral capabilities which would enable identification of specific chemical substances (such as minerals) by their spectral reflection properties (spectral lines of a few nanometers width). The above specifications for digital cameras for Open Skies use are now met by most commercial digital aerial cameras which dominate the market for non-military aerial remote sensing. Cameras with a so-called Bayer filter, which collect images in three spectral bands on one sensor matrix, are allowed as well.

When introducing new sensors into Open Skies, determination of the ground resolution is a key issue. For digital cameras and thermal imaging sensors, ground resolution depends on flight altitude: the lower the altitude, the better the resolution. Consequently, in order to ensure that images are at a resolution allowed by the treaty, the corresponding flight altitude has to be determined in advance. To do this, a target which contains groups of bars of increasing width is over flown at different altitudes. Targets for digital aerial cameras consist of alternating black and white bars. Targets for thermal sensors consist of alternating warm and cold bars. Observers from different states parties can then analyse images of the target taken during the flights to determine the group of narrowest bar width discernable by the sensor (a process known as ‘resolution reading’). This enables the appropriate flight altitude to be established and the corresponding camera configuration to be certified. The procedures of resolution reading from digital images are specified in decision OSCC/DEC/8/10.

Since a ‘certification event’ is limited by treaty to seven days, time constraints and bad weather can hamper the (statistical) accuracy of the result. The decision on certification seeks to mitigate this constraint by requiring states parties to establish an extensive database of resolution values at different flight altitudes for each particular camera configuration in advance and to communicate the results at least 60 days before the multinational certification event. The one week certification event would then only be used to cross check the results with a small number of flights and to establish the minimum allowed altitude for observation missions.

A further decision of the OSCC specifies the formats for data exchange between parties (OSCC/DEC/9/10). Raw image data must be erased once they have been processed and distributed in the official exchange format in order to make sure that all parties have access to the same kind of images.

Other issues
During the conference, a number of other issues were discussed, including the so-called ‘other applications’ and also the accession of additional member states. The preamble of the treaty envisages the ‘possible extension of the Open Skies regime into additional fields such as protection of the environment’, though this option has never been operationalized in treaty decisions. However, several states have performed disaster monitoring flights on a national or bilateral basis. The US Open Skies aircraft flew extensive disaster-monitoring and disaster-relief support missions in the aftermath of hurricanes Katrina and Rita in 2005, and, most recently, after the earthquake in Haiti earlier this year. However, these were nationally-mandated flights lying outside the treaty’s provisions. There is little chance that post-disaster or environmental monitoring flights will become part of treaty implementation within the present framework of quota flights (which gives each party the right to perform an agreed number of flights over other parties). Disaster monitoring with Open Skies aircraft will remain an exception in view of available national capabilities like radar satellites and other civilian and military observation aircraft.

The most recent accession to the treaty was that of Lithuania in 2005. Cyprus’ application is pending since 2002, due to a veto by Turkey. This situation was one of the few controversial issues at the conference. After all parties had agreed on a final document, an interpretative statement on behalf of 32 states parties was read. The statement expressed explicit support of Cyprus’ application and the hope that consensus on the application can be obtained in the near future. In response, the Turkish delegate expressed ‘dismay that an issue that lies outside the scope, mandate and purview of the Open Skies bodies and of the Review Conference has been brought to the Closing Session’.

The final document mentions also ‘that the Treaty might serve as a model for aerial monitoring regimes in other regions of the world in order to promote security and stability.’ The document states that the states parties are ‘prepared to enter into dialogue with interested parties in order to share experience, to exchange general information about the Treaty and its benefits and to provide advice on cooperative aerial observation’. In practice, there has been little activity lately in this direction. Between 1996 and 1999, the United States undertook various initiatives by displaying its Open Skies aircraft in Japan, China and in South America and by briefing governments on the Open Skies treaty in Eastern and Southern Asia as well as in South America. These activities were not followed up under the Bush administration. Currently, the Obama administration and governments of other states parties are open to exchanging general information about the treaty worldwide. It remains to be seen to what extent governments in other parts of the world come to appreciate the Open Skies model as a strong confidence-building measure supporting regional transparency in security matters—and to what extent they consider applying a similar arrangement in their own regions.

In summary, the conference proceeded fairly harmoniously, especially in comparison with the 2005 Review Conference (which failed to reach consensus on a final document due to a Turkish veto on the Cyprus accession issue). Open Skies officials and practitioners have learned to work with each other. In addition, it is clear that both the US and Russia, as well as the other parties, adhere to the treaty`s objectives and substance, and see it as an asset. There was, however, no discussion of the larger political environment of Euro-Atlantic security in which the Open Skies Treaty operates. The treaty will, nevertheless, continue to play a significant part in the monitoring of conventional arms control in Europe as well as in the area of confidence and security building, especially given the enhanced sensor set that can now be used.

Hartwig Spitzer.
Hartwig Spitzer is the spokesperson for the Center for Science and International Security (CENSIS) and an associate member of the Carl Friedrich von Weizsäcker Center for Science and Peace Research at the University of Hamburg, Germany. He is also a professor in the Department of Physics at the University of Hamburg. He has attended the 2005 and 2010 Open Skies review conferences and participated in sessions of the Open Skies Consultative Commission’s Informal Working Group on Sensors since 2005.


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