SESSION III. UAV Payloads and Data Dissemination Ltc.Dr.Erdal Torun (TLFC Tech. & Prj. Mng. Department-Türkiye)

Transcription

1 SESSION III UAV Payloads and Data Dissemination Ltc.Dr.Erdal Torun (TLFC Tech. & Prj. Mng. Department-Türkiye) LOROP Systems and Operational Benefits of Dual Band LOROP Systems Mr. Larry Maver-Mr. Tony Costales (Raytheon Systems Company- USA) Operational Requirements and System Constraints of Automatic Landing System for UAVs Mr.H.Anthony Hoskins (Sierra Nevada Cooperation-USA) Operational Concepts of UAVs for Tactical Recce BGen.Doron Tamir (Ret.)-Mr. Shumel Feldman, (Israel Aircraft Industries, Malat Division-Israel) The Use of Adaptive Approaches in Manoeuvring Target Tracking Dr. Murat EFE (Ankara Univ., EE Dept.-Türkiye)

2 UAV PAYLOADS AND DATA DISSEMINATION Ltc. Dr. Erdal TORUN Technical and Project Management Department Turkish Land Forces Command Yücetepe, ANKARA Tel: +90 (312) Fax: +90 (312) E/Mail: 1. ABSTRACT The types of the payloads carried by the air vehicle are defined by the different mission requirements of the user. Recognition, intelligence, surveillance and target acquisition (RISTA) payloads are the most common used by UAV systems and are of the highest priority for most missions. The primary payloads technology for RISTA purposes are Electro Optic (EO), Infrared and synthetic Aperture Radar (SAR) sensors. Resolution, area to be searched, dimensions, cost-effectiveness, air vehicle s performance and tactical requirements are some of the important parameters to define payloads specifications. Having payload images at Ground Control Station is not sufficient requirement itself. After receiving the raw data, evaluated information must be disseminated to the operational units at the time. This paper deals with the UAV payload specification and choosing the optimum payloads for the mission requirements. Data link and data dissemination requirements and some applications will also be reviewed. An

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4 assessment will be given to have efficient surveillance and reconnaissance capabilities and real time data transmission. 2. INTRODUCTION There have been increasing demands in modern world to use UAV systems as Intelligence, Reconnaissance, Surveillance and Target Acquisition Systems. Although requirements for UAVs change based on the missions to be carried, expectations are generally similar for each type. Cost-effectiveness, reliability, maintainability, usefulness and operational availability are some of the requirements that all systems should have. Besides these, all UAV system should also fulfill certain basic requirements, which will be given in next sections. These requirement help to define the UAV system specifications in terms of the performance parameters of the basic subsystems, such as air vehicle, ground control station, payloads, data link, and C4I systems and support equipment. Performance parameters are closely interrelated and usually shape these subsystems. At the beginning of the program definition phase, requirements are always beyond the technological advances [1]. Requirements and system specifications for payloads, data link and C4I systems are considered in next sections of this paper. 3. UAV TASKS AND BASIC REQUIREMENTS Some of the today s and future's tasks for UAVs can be listed as follows; Reconnaissance, intelligence, surveillance and target acquisition Communication and navigation EW/Jamming Mine Countermeasure Chemical/Biological reconnaissance Mapping Suppression of enemy air defenses (SEAD)

5 Fixed and moving target attack

6 All UAV systems should fulfill certain basic requirements, as outlined below; Performing efficient surveillance and reconnaissance missions for the armed forces Day and night operations Operating in a wide range of weather conditions Various altitude operation Beyond Line-of-Sight (BLOS) operation Real-time operation Multi-mission capability, etc. 4. AIR VEHICLE PERFORMANCE PARAMETERS Radius of action is defined as the maximum distance that the UAV can travel away from its base along a given course with normal mission payload and return without refueling. This distance is directly dependent on the level of military unit that will operate the system and will ideally cover their area of interest. The endurance at the radius of action is an important parameter that defines the coverage of the air vehicle at the specified loiter speed, typical operating altitude and sensor properties. Endurance is mainly dependent on the air vehicle aerodynamic design, and fuel amount carried. Fuel increase capacity is usually a problem since the space and weight available for fuel is limited. Typical operating altitude can be defined as the altitude where the specified payload performance (e.g. image quality) and coverage can be obtained with the desired mode of operation (through data link or autonomous recording). Higher altitudes are desirable for better coverage, survivability and line-of-sight for data link operations. The cruise and maximum speed is dependent on the engine power and aerodynamic design of the air vehicle. As mentioned before, a high endurance requirement is conflicting with a high speed requirement since high endurance designs usually have efficient small engines (compared to their size) and big

7 wings with high drag. Cruise speed requirements are driven by the timeliness of mission.

8 Loiter speed is usually the optimum speed for endurance and is somehow slow (close to the stall speed). The loiter speed directly affects the payload coverage area. Climb rate is related with the speed and altitude performance of the air vehicle. It is an operationally important parameter especially when the terrain to clear is close and/or steep. A high climb rate also improves the survivability of the air vehicle. 5. GROUND CONTROL STATION The Ground Control Station (GCS) is the operational control center of the entire UAV system. It controls the launch, flight and recovery of the air vehicle, receives and processes data from the payloads, controls the operation of those payloads (often in real time), and provides the interface between the UAV system and the outside world [2,3] GCS should be scalable, modular, flexible, be capable of executing maintenance software and displaying appropriate status results, capable of operation within the specified environmental conditions, easily deployed and transported. It should also provide open system architecture and have ergonomically designed operator controls and displays. 6. PAYLOADS The term payload is referred to the equipment that is added to the UAV for the purpose of performing some operational mission. In other words, the equipment for which the basic UAV provides a platform and transportation. This excludes the flight avionics, data-link and fuel. Using this definition, the payload capacity of a UAV is a measure of the size, weight and power available to perform functions over and above the basic ability to take-off, fly around and landing. The types of payloads carried by the air vehicle are defined by the different mission requirements of the user. Reconnaissance payloads are the most common used by UAV systems and are of the highest priority for most users. The primary payload technologies for reconnaissance mission are Electro- Optic (EO), Infrared and Synthetic Aperture Radar (SAR). The key issues

9 associated with them are; having the resolution to see far enough and at the same time over a wide enough area, and having a payload that is small, light,

10 low power consumption and at an affordable price, such that a UAV can carry it for a period long enough to satisfy the end users needs. Additionally, in conjunction with other sensors, such as range finders, and the UAV s navigation system, the payload may be required to determine the location of the target with a degree of precision that depends on the use to which the information will be put [2,3,4]. For the users and designers of UAV systems, choosing the optimum payload for the mission requirements is of prime importance. The relative advantages of the sensor types and their potential for satisfying a range of common mission goals should be evaluated. Technology is advancing rapidly in many sensor and signal processing fields and the probability (potential) for new solutions to current problems should be considered. Some mission requires putting and controlling more than one payload at same time. But AV size, data link and interface limitations and GCS control capabilities allow having this request. Whatever the operational requirements are for payloads, the other important point is to have payload modularity. In another words, different types of payloads such as reconnaissance, Electronic Warfare (EW), mine detection, NBC, meteorology and etc. should be easily plugged in the AV without SW and HW modifications. Having payload data in GCS is not sufficient itself. Evaluated data should also be disseminated to the active units in real time through the well-established C 4 I network. 7. DATA-LINK The data-link is a key subsystem for any UAV system. It provides two-way communication, either upon demand or a continuous basis. An up-link provides control of the air vehicle flight path and commands to its payloads. The down link provides both a low data rate channel to acknowledge commands and transmit status information about the air vehicle and a high data rate channel for payload data such as video and radar.

11 The data-link typically consists of two major subsystems; the Air Data Terminal (ADT, the portion of the data-link that is located on the AV) and the Ground Data Terminal (GDT, the equipment on the ground).

12 On a battlefield the UAV system may face a variety of EW threats, including direction finding used to target artillery on the ground station, anti-radiation munitions (ARMs) that home on the emissions from the GDT, interception and exploitation, deception and jamming of the data-link. It is highly desirable that the data-link provides as much protection against these threats as reasonably can be afforded. Depending on the mission and scenarios, the desirable attributes for a UAV data-link can be summarised as follows [1]: Worldwide Availability of Frequency Allocation: Operate on frequencies at all locations of interest to the user in peacetime as well as being available during wartime. Resistance to Unintentional Interference: Operate successfully despite the intermittent presence of in-band signals from other RF systems. Low Probability of Intercept (LPI): This is highly desirable for the up-link, since the GCS is likely to have to remain stationary for long periods of time while it has air vehicle(s) in the air, making it a target for artillery or homing missiles if it is located. LPI can be provided by frequency spreading, frequency agility, power management, low duty cycles and using directional antennas. Security: Unintelligible if intercepted, due to signal encoding. As a general rule, it appears that security is of only marginal value in a UAV data-link. However, some intelligence missions could introduce security requirements. Resistance to Jamming: Operate successfully despite deliberate attempts to jam the up and/or down link. The overall priority of anti-jam capability depends on the threat that the UAV is expected to face and the degree to which the mission can tolerate jamming. Resistance to Deception: Reject attempts by an enemy to send commands to the air vehicle or deceptive information to the GDT. Deception of the up-link would allow an enemy to take control of the air

13 vehicle and either crash, redirect, or recover it. Deception of the up-link only requires getting the air vehicle to accept one catastrophic command

14 (e.g., stop engine, switch datalink frequency, change altitude to lower than terrain, etc.). Deception on the down link is more difficult, since the operators are likely to recognize it. Resistance to deception can be provided by authentication codes and by some of the techniques that provide resistance to jamming, such as spread-spectrum transmission using secure codes. Line-of-Sight range constrains, AV/GCS relative position, link availability, data characteristics, EW environments and installation requirements are the main characteristics to define data link for a UAV system [2]. Data link can be established by hub/prime site deployments and utilization of relays (ground, airborne, satellite). Operational cost, missions, deployment area and above characteristics are important parameters to choose the means that extend the mission radius. Since users never prefer link loss between air vehicle and ground control station during real time operations, both telemetry data and video link should be well established. Since the interaction between the data-link and the rest of the UAV system is complex and multifaceted, the design tradeoff between them should occur early in the overall system design process. This allows a partitioning of the burden between the data-link, processing in the air and on the ground, mission requirements, and operator training. 8. DATA DISSEMINATION The purpose of UAV is to provide high quality timely data to the place where it provides the greatest military advantage. Data dissemination is done either directly from A/C or GCS after evaluation to operational units or headquarters. Distribution of payload data real time/or near real time from GCS to operational units is needed in order to maximum benefit from UAV missions. The GCS must be able to disseminate UAV payload data to a variety of users via C4I systems in digitised battle space environment. The GCS must be able to exploit the full performance potential of payloads consistent with mission tasking. Data reception can either be secondary (indirect receipt of imagery and/or data) or direct (direct line of sight with the UAV or a relay device having direct line of sight with the UAV.) Payload data can be disseminated to user by RVT (Remote Video Terminals) or C4I Systems.

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16 Raw target data together with telemetry info usually are not transferred to the end users. UAV RISTA data should be normally processed at intelligence station, and then send processed data to C2 station through the C4I interface. Air defense data obtained by UAV is sent to RAP facilities directly, where all source information is correlated. UAV data dissemination capabilities are inherently flexible to support the operations 9. CONCLUSION In recent years, the high demand for UAVs has resulted in quest for technological advancements expected from these systems. Different payload types are becoming popular for UAVs. AVs and payloads should be considered for cost-effectiveness. Near-real time pictures and formatted data are useful for end users, not near-real time data REFERENCES [1] E. TORUN, UAV Requirement and Design Consideration, RTO SCI Panel Symp, 26 April 1999 Ankara [2] Pre-Feasibility Study on UAV Systems Interoperability, NIAG SG-53, Feb [3] Introduction to UAV Systems, Paul G. Fahlstrom, Thomas J. Gleason, Dec [4] Remotely Piloted Vehicles, Twelfth International Conference, Bristol, UK..

17 This paper represents the views of the author; it does not necessarily represent the official views of the Turkish Armed Forces.

18 BIOGRAPHY LTC Dr. Erdal TORUN has graduated from the Military War Academy and Electrical Engineering Department of Istanbul Bosphorous University in 1981 and 1984, respectively. He received his Ph.D. degree from the Ankara University and he started working at the R&D Department of the Turkish MOD as project manager. During the same period, he work as an academic instructor and gave lectures in the Military War Academy. LTC TORUN joined at Communication Research Center in Ottawa, Canada in 1994 for one year. He is currently Chief of the Electronics Branch of the Technical & Project Management Department of the TLFC.

19 LOROP Reconnaissance Systems: The Operational Benefits of Dual-Band / Multi-Mission LOROP Sensors Larry Maver Raytheon Systems Company 4 Hartwell Place Lexington, Massachusetts USA lamaver@west.raytheon.com 1. ABSTRACT Optical reconnaissance sensors are undergoing a revolution from primarily daytime-only film camera based systems to 24-hour, day/night digital sensor systems. The changing world environment, in terms of technological advances and new operational requirements, has brought about this transition. There is a worldwide trend to replace film LOROP (LOng-Range Oblique Photographic) cameras with dual-band E-O/IR (electro-optical/infrared) systems. This paper reviews the motivations for these changes and presents examples of the benefits of these new generation systems. 2. INTRODUCTION Before discussing the advances made by modern LOROPs, it will be useful to consider the general classes of mission types. Airborne reconnaissance (recce) sensors are generally categorized by their mission type and altitude

20 range as illustrated in Figure 1. Descriptions and examples of these categories follow.

21 Low Altitude Overflight Nadir ± 1000 ft Medium Altitude Overflight/Standoff Nadir ± 5-8 nm High Altitude Standoff 5-50 nm Figure 1. Traditional Recce Mission Categories Low Altitude Overflight: High speed, low-altitude penetrating missions are employed in high threat (wartime) environments to collect imagery directly over targets (nadir ± 5,000 ft swath width). Altitude ranges of 200-3,000 ft are typical, as are high velocity/range (V/R) ratio operation. Due to the short range to target and high V/R, low altitude sensors are based on short focal length optical systems. In the United States, the US Marine Corps ATARS (Advanced Tactical Air Reconnaissance System) used in the F-18 platform is one example of a lowaltitude system. The daytime sensor is the Low Altitude Electro-Optical (LAEO) sensor (1-inch focal length). For day or night, D-500 Infrared Line Scanner (7.3-inch focal length) can be used.

22 Medium Altitude Overflight/Standoff: Medium altitude missions are used to collect imagery for both overflight and standoff missions. In general, medium altitude operations are in the range of 2,500-25,000 ft. In high threat environments, an aircraft would fly a lowaltitude penetration mission, pop-up to medium altitude to quickly image the area of interest, and then revert to low-altitude for safe exit. In lower threat environments, the platform may fly at medium altitude and image at either nadir (overflight) or at left, right or forward oblique (standoff). Medium altitude sensors employ focal lengths generally in the 6-18 inch range. In the ATARS sensor suite, the 12-inch focal length Medium Altitude Electro- Optical (MAEO) sensor is utilized for side looking oblique (pushbroom) imaging in the daytime. The Predator UAV (Unmanned Aerial Vehicle) utilizes day and night video sensors with zoom optics. High Altitude Standoff LOROP sensors systems are utilized to image at long-range in peacetime as well as in threat environments. The high altitude category is generally applied to systems typically operating in the 20,000-50,000 foot range (and above on special mission platforms). The fundamental design characteristic to support long-range operations is focal length. LOROP s employ focal lengths of 36- inches or greater. LOROP collections are generally at standoff ranges from 5 to 10 miles out to the horizon. In the United States, the only operational LOROP system is the SYERS (Senior Year Electro-Optical Sensor) operating on the U-2 aircraft. The Global Hawk UAV is also high-altitude standoff platform utilizing a 70- inch focal length sensor in both the visible and infrared (IR) spectrums, in addition to integrated synthetic aperture radar system. Mission Requirements During the Cold War, the predominant tactical recce mission anticipated was low-altitude overflight to operate in a wartime/high-threat environment. Following the Cold War, and with the experience of Desert Storm, military recce requirements underwent a change in emphasis.

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24 Most recce operations today will occur during peacetime. Overflying a neighboring country is unacceptable; a border surveillance mission must be flown in order to collect intelligence information. Long-range standoff (long focal length) systems are essential to collect useful imagery. Peacekeeping missions (Bosnia, Southern Watch) are usually restricted to a minimum altitude (e.g. 10,000 feet), therefore also mandating longer focal length sensors to achieve high quality imagery. Still, recce capabilities must be available for crisis and wartime environments. Both low altitude overflight and medium altitude (pop-up) systems will be used in high threat environments, as will high altitude standoff sensors which increase survivability by collecting imagery far from groundbased threats. Flexibility to reprogram missions is an implicit requirement in order to adjust collection strategies in a dynamic environment, for example to collect Targets of Opportunity. Systems must be interoperable. Film-based systems are typically single stove-pipe solutions imagery is collected and exploited within a single squadron. Use of the data outside of that unit may be difficult to implement in a timely fashion. Today s operations require a fused data environment to allow data to be shared within the services as well as with Coalition partners in NATO operations, for example. NATO Standard Agreements (STANAGs) have been developed to define the formats for interoperable data format, recorders and data links. Day/night capable systems with near real-time intelligence dissemination are fundamental requirements. An adversary s operations can take place at any time of day or night. It is an essential requirement to detect and monitor such exercises on a 24-hour basis to allow commanders to react within an opponent s decision cycle. To do so, relevant information must get to decisionmakers and the warfighter in a timely manner. Film systems can only support daytime operations and require return-to-base and chemical processing before any intelligence can be derived. Such timelines are too lengthy for modern operations. Digital intelligence data from an airborne recce system to users can be accomplished in near real-time using airborne data links and ground receive terminals. Secondary dissemination of

25 intelligence reports and selected imagery to field commanders can be achieved over lower bandwidth ground communications.

26 Although the recce responsibility typically belongs to the military, there is a growing need to supply data to political and civilian decision-makers. Border control, counter-terrorism, smuggling interdiction are examples of national requirements which can be supported by recce systems, in particular real-time systems that can provide law enforcement authorities the ability to quickly react. Disaster assessment can be conducted on large scale, at day or night, in order to provide authorities the best information to make humanitarian assistance decisions. LOROP System Design Optical Sub-Systems Most film cameras used refractive lenses alone to image the ground. Refractors allowed broad area coverage to be achieved from low altitude as such lenses could economically provide wide-fields-of-view. Although refractive optics can be used with electro-optical focal planes, normal optical lenses will not pass infrared energy. Thus, film cameras can be upgraded by replacing the film cartridge with CCD (charge coupled device) detectors, but only daytime imaging can accomplished with this method. An additional consideration is that a lens optimized for a film camera is rarely an optimum design for a digital E-O system. As longer-range performance is required today, designers of modern systems typically select catadioptric (mirror plus refractive lens) or pure reflective imaging systems. Mirror systems offer several benefits: Substantial savings of weight in large aperture, long focal length systems Mirror systems are more amenable to folding the optical path to reduce length and volume Less sensitive to thermal perturbations Mirror systems show no chromatic aberrations, thus allowing wide spectral bandwidths to be collected by a single optical system (e.g. visible and infrared)

27 Focal Plane Assemblies Both line and area array focal plane assemblies are available to detect visible and infrared energy. Curiously, film has been used both as an effective area array and a line array in LOROP cameras. In a framing camera, a single image could comprise a 4ºx4º field of view, exposed at one time onto film. Upgrading such film cameras to E-O, an area array CCD is used to maintain this same format. In pushbroom and sector scan (whiskbroom) cameras, film is continually exposed through a variable slit while the film travels behind it. Line array CCD s employ the same operation, using variable Time, Delay and Integration (TDI) to vary the effective exposure in like manner to the variable slit. Either a line or area array can be used to collect LOROP imagery. Figure 2 illustrates a pan-scanning collection system, in which the sensor scans the ground scene perpendicular to the flight path. The upper rectangles indicate the operation of a dual-area array system. Individual frames are collected in what is called a step-stare method. The area arrays are focused (held constant) on a single ground area for the duration of an exposure. A backscan mirror or prism assembly may be used to keep the line-of-sight stationary during the integration period. Once the exposure is completed, the arrays are projected to the next ground position, overlapping the first exposure by a small amount to maintain continuous coverage. A line array provides a continuous scan of the same ground area, as illustrated by the lower region. When the image is reconstructed on the ground, both images will appear to be a continuous scan to the viewer.

28 Figure 2. Pan-scan collection system can use area array or line array to collect the ground scene. Dual-Band LOROP Design Figure 3 illustrates the fundamental components of a dual-band LOROP. A common, all-reflective front-end optical system collects reflected (visible) and emitted (infrared) energy of the ground scene. A beam splitter behind the optics separates the visible and the infrared wavelength energy and directs each to their corresponding focal plane assemblies. There may be additional optics used in the individual visible and infrared optical chain (e.g. field flattener lens).

29 Ground Scene Front-End Optics Beam Splitter Visible FPA IR FPA Figure 3. Fundamental components of dual-band sensor using common front-end optical system. Benefits of Dual-Band E-O/IR LOROP Systems A fundamental benefit of a digital sensor system, as compared to a film system, is timeliness. Using a data link, time-critical information can be collected and transmitted to users in near-real time. Even without an airborne data link, upon landing a digital tape or solid-state memory device with the collected imagery can be removed from the airborne system and brought to an exploitation workstation for immediate use.

30 There are a number of other benefits that can be realized with a dual-band LOROP that result from the spectral content of the imagery. Examples are presented below. Additional Haze Penetration Film is sensitive from approximately 0.4 to 0.7 µm, whereas E-O (silicon CCD detectors) are predominantly sensitive in the 0.6 to 0.9 µm region. Atmospheric haze is predominantly blue (0.4 to 0.5 µm), as the shorter wavelengths are scattered more than longer. Haze is a non-image forming light, that is a uniform radiance imposed over the image forming light (from the ground scene). The effect of haze is a reduction in the contrast of the ground scene image, which equates to a reduction in the signal-to-noise ratio (SNR). The SNR reduction causes degradation in image quality. Film simply cannot record wavelengths from just above 0.7 to 0.9 µm, as can an EO detector. This wavelength region is referred to as the near infrared, or NIR. There is significant image forming NIR energy from a ground scene that leads to greatly improved contrast and quality in an EO image. Figure 4 illustrates this difference. The near IR (right hand image) penetrates the haze better than visible wavelengths, thus better contrast between objects in the scene and increased interpretability.

31 Figure 4. Images looking at long range across valley. Lefthand image is 0.4 to 0.7 µm spectral bandpass (equivalent to film), whereas righthand image is µm (equivalent to E-O CCD), illustrating the improved contrast in the near IR wavelengths. Photographs courtesy of Duncan Technology. Short-Wave Infrared Infrared focal plane arrays, such as Indium Antimonide (InSb) detectors, provide sensitivity in both the short-wave (1.2-3 µm) and mid-wave infrared (3-5 µm) wavelengths. The short-wave infrared (SWIR) spectrum can provide still additional haze penetration with respect to a visible CCD. This effect is most pronounced under poor imaging conditions that would be encountered under very hazy daytime conditions or at very long range. The images in Figure 5 were collected under clear and hazy conditions to illustrate this effect.

32 Figure 5. Comparison of visible wavelength (left column) and SWIR images (right column) acquired under clear (top row) and poor atmospheric conditions (lower row). Images courtesy of Raytheon Systems Company. The upper images were acquired from a 46 nautical mile slant range under very clear (46 nautical mile meteorological visibility). The top left image was collected in the µm spectral range and top right image in the µm

33 SWIR bandpass. Under these conditions, there is little difference in the image quality. In the lower images, the meteorological visibility had dropped to 9 nautical miles. Slant range to target was 35 nautical miles. Under these conditions, the visible E-O image (lower left) is very low contrast and as a result, very little information can be extracted from the image. In the lower right SWIR image, contrast is much greater as is the information content. It should be noted that only certain spectral regions within the full SWIR range provide windows through which haze can be effectively penetrated. Mid-Wave Thermal Information The mid-wave infrared (MWIR) can be used collect imagery in both the day and night. At night, MWIR detects emitted thermal energy. The amount of energy emitted is a function of an object s temperature and emissivity. With a MWIR detector, a dual-band LOROP can image at any time of the day. In most situations, the MWIR will be used at night, but it can also be used to provide additional information during the day. Figure 6 illustrates a unique characteristic of MWIR imagery. It is possible to see the level of fuel in the POL storage tanks based on their residual thermal signature. The dense fuel oil, which would be heated during the daytime, retains some of that heat throughout the night. The sides of the tank cool more quickly at night than the fuel, and are lighter in appearance in the thermal IR image. The tops of the tanks appear black as they are reflecting the cold sky.