The RAMOS (Russian-American Observation Satellite) Program

RAMOS program logo.

The RAMOS (Russian-American Observation Satellites) program was a cooperative project between the US and Russian Federation.  Sponsored by BMDO (Ballistic Missile Defense Organization which was renamed the Missile Defense Agency or MDA in 2002), the program originated in 1992 as a means of fostering cooperation between the military establishments of the former Cold War adversaries.

While the political objective of the RAMOS program was to engage Russia in a cooperative defense-related space program, the primary technical objective was to conduct joint research and development on new approaches to improve space-based early warning capabilities especially enhancing the ability to detect dim targets and reduce false alarms. Secondary technical objectives included performing observations of a more environmental nature in an attempt to broaden the appeal of the program beyond defense interests.

The PDR (Preliminary Design Review) for the American instrument payload was successfully completed in May 2002 followed by the joint PDR with the program’s Russian partners for the space and ground segments in June 2003. While work was progressing towards CDR (Critical Design Review) with a launch planned by 2009, the RAMOS program was cancelled in 2004 by MDA.

In the following sections, the RAMOS science objectives and experiments are outlined followed by a description of the pair of spacecraft and their instruments as designed to meet those objectives.  Finally, there is a section describing the joint near-term experiments performed by the American and Russian RAMOS teams between 1995 and 1999 in support of the program involving existing spacecraft and aircraft.

RAMOS Science Objectives & Experiments

To meet the technical objectives of the RAMOS program, seven generic experiment categories were formulated by the Russian and American teams during the course of the 1990s. These proposed experiments and how RAMOS would meet their objectives were reviewed as part of a Conceptual Design Review (CoDR) in January 1998 and were subjected to additional reviews including a Joint Independent Science Review in May 2000.

Diagram illustrating the major RAMOS system components. Click on image to enlarge.

Moving Object Experiment (MOE): The objective of this experiment was to demonstrate the ability to observe a post-boost warm body (i.e. a warm “target” after its booster had burned out) against the hard Earth background and accurately reconstruct its trajectory in three dimensions. Dedicated rocket targets would be launched from instrumented ranges in the US and Russia with the objectives met through post-flight processing of the collected data.

Multi-Spectral & Stereo Backgrounds (MSB): In this experiment, the goal was to acquire spatial and temporal radiance image databases of Earth backgrounds taken simultaneously in multiple wavelength bands. Of primary importance was the direct comparison of images acquired in the 5.4 to 7.2 μm water vapor band and the 4.23 to 4.43 μm CO₂ band. These data would then be used for constructing future models as well as simulating the performance of the next generation of space-based sensors.

Background Effects of Solar Scatter (BES): The objective here was to characterize polarized solar scattering from water and ice clouds as well as investigate the multi-spectral properties of solar glints. These polarization observations would be performed primarily in the SWIR (shortwave infrared) and visible wavelengths.

Short Duration Events (SDE): Here we would perform stereo observations of short duration events at high frame rates using a range of wavelengths to demonstrate the ability of accurately locating them under a range of conditions. Short duration events would included ignition spikes from rockets as well as their subsequent burns, artillery engagements and explosions of various kinds.

Fast Changing Events (FCE): For this experiment, the goal was to demonstrate that fast changing events could be detected, observed and characterized from low Earth orbit. Primarily an environmental investigation, this included observing large fires, characterizing the extent and volume of volcanic plumes and estimating the strength of tropical cyclones.

Wind Velocity Distribution (WND): The objective of this environmental experiment was to use visible band stereo data to demonstrate the ability to determine the three-dimensional wind velocity on a worldwide basis using remote sensing data.

Water Vapor Profiles (WVP): Here the objective was to characterize the three-dimensional distribution of water vapor concentration in the lower ten kilometers of the atmosphere using SWIR and MLWIR (mid-long wave infrared) spectrometers.

RAMOS Spacecraft & Instruments

In order to meet the jointly agreed science objectives, a pair of co-orbiting satellites would be used to make the required stereo observations with a nominal 100-meter pixel footprint and with sufficiently accurate pointing information to create three dimensional reconstructions of an observed scene to an altitude accuracy of on the order of 100 meters. Originally it was envisioned that the RAMOS constellation would consist of one American and one Russian satellite with each side responsible for the instrumentation of their own satellites. But in July 2000, BMDO altered the architecture of the constellation to a pair of Russian-built satellites with each carrying a suite of Russian- and American-built instruments.

Diagram of the RAMOS satellite based on the Russian Yacht universal space platform. Click on image to enlarge.

In this final form, RAMOS consisted of a pair of co-orbiting spacecraft based on the Russian “Yacht” universal space platform with an estimated mass of 1,200 kilograms each. The satellites were to be launched six months apart into a high-inclination, 500-kilometer orbit from the Plesetsk Cosmodrome on separate Rokot launch vehicles. The satellites would control their orbits using onboard propulsion systems to maintain a nominal separation of 500 kilometers that could be varied from 50 to 2,600 kilometers to meet the objectives of different experiments over a range of viewing geometries. The spacecraft would have been controlled from a joint operations center located in Moscow. The minimum mission length was two years with the goal that the spacecraft could continue to function for at least five years to provide a large archive of stereo data under a wide range of conditions for future study.

The RAMOS payload sensor footprints shown in relation to each other and the available field of regard (FOR). Click on image to enlarge.

The pair of RAMOS satellites would carry nearly identical payloads of sensors primarily grouped behind two slaved pointing mirrors that moved in concert to keep the field-of-view (FOV) of the various instruments co-aligned. These pointing mirrors would allow the instruments using them to point anywhere inside a 30.5° field-of-regard (FOR) to track the region of interest and provide flexible simultaneous measurements during the course of an observation session. The whole satellite could be rotated to move this FOR over 4π steradians so that any point could be observed outside of a solar exclusion zone. The pointing system would have also been equipped with sunshades to allow observations to be made at very high scattering angles.

Diagram showing the configuration of the RAMOS instrument suite. Click on image to enlarge.

Infrared Radiometer & Infrared Spectrometer (IRR & IRS): Behind the first pointing mirror was the primary instrument of the payload: a two-channel IR imaging radiometer, the IRR, designed and to be built by SDL. It consisted of a pair of co-aligned 128 by 128-pixel detector arrays cooled to 77° K to improve sensitivity. The arrays would have had about a 140 μrad pixel footprint yielding a total field of view (FOV) of about 1.0°. The two arrays would allow a pair of simultaneous images to be acquired in the SWIR and MLWIR over a wavelength range from 1.5 to 7.5 μm.

The IRR packages on each RAMOS satellite were of slightly different designs. The IRR on one satellite was also designed to operate in a mode to act as a SWIR imaging polarimeter.  The IRR of the other satellite also included an imaging spectrometer, the IRS, with its own pair of dedicated 128 by 128-pixel detector arrays that together covered the 2.3 to 7.5 μm spectral range using diffraction gratings. The 1° entrance slit of the IRS was offset 1° from the center of the IRR FOV.  With the IRS staring in a fixed direction, the motion of the satellite would build up hyperspectral image working in a push-broom mode.

The RAMOS IR spectral bandpasses shown in comparison with the typical spectral radiances expected from Earth’s atmosphere (daytime and nighttime) and a 300 K blackbody.  Click on image to enlarge. (Visidyne)

Visible Camera (VC): Behind the second mirror was a set of three Russian-built cameras. The first was a visible high-speed camera, the VC, with a 3.1° FOV operating at frame rates as high as 100 Hz.  It was designed to provide visible band images of the observed scene and was capable of recording quickly changing scenes or events. The VC had a 512 by 512-pixel array with four different filters that together covered wavelengths in the 400 to 960 nm range .

Visible Matrix Camera (VMX): The second Russian instrument was a wide-field visible matrix camera system, the VMX, that used five cameras with overlapping fields to provide a total FOV of 3.5° by 30°. The VMX would be fitted with RGB filters as well as others of environmental interest that together would cover wavelengths from 460 to 960 nm. The VMX could acquire continuous image swaths to provide a regional context of what was being observed by the other instruments with narrower FOVs.

Ultraviolet Radiometer (UVR): The final Russian instrument was a multi-filtered, two-channel ultraviolet imaging radiometer, the UVR. One channel of the UVR used a 290 by 384-pixel array and would cover wavelengths ranging from 200 to 300 nm with a 1.44° by 1.92° FOV. The second channel employed a 576 by 576-pixel array that would cover from 300 to 400 nm with a 1.47° FOV.

The RAMOS UV and visible instrument spectral bandpasses shown in comparison with the typical spectral radiances expected for the sunlit clouds for two scattering angles. Click on image to enlarge. (Visidyne)

Visible Push-Broom (VPB): The final instrument was a visible-band push-broom imager, the VPB, designed and to be built by Visidyne. Unlike the other instruments that used the pair of pointing mirrors, the VPB was mounted on the spacecraft bus with a fixed 30° wide FOV aligned at the bottom edge of the FOR of the instruments using the pointing mirrors. With a cross-track pixel footprint of 64 μrad, it would use the orbital motion of the spacecraft to create its images in a push broom mode. It was designed to make measurements of polarization and cloud top altitude independently of the stereo observations (but with much less accuracy) by comparing the radiances in two selected wavelengths.  This instrument also provided a wide FOV context image of the area being observed by the other instruments to complement the Russian VMX images.

RAMOS Near Term Experiments

As the design and architecture of the RAMOS constellation and its ground segment were being developed, it was decided early in the program that a series of field science campaigns would be performed to gather data on various types of cloudy scenes. The goal of these near term experiments was to develop the mechanisms needed to plan experiments, coordinate operations as well as share data and analysis results between the American and Russian teams during joint data collections. In the process, these near term experiments would acquire data needed to refine the program’s science objectives and validate performance requirements for the instruments to be carried by the RAMOS satellites. I was one of the key members of the American science team responsible for the processing and analysis of the data collected from these joint experiments including the development of the algorithms required to create three-dimensional, multispectral scene reconstructions using stereo data.

The first near term experiment campaign took place in 1995.  This campaign involved the Russian Resurs-O1 satellite and the USAF/NASA ARES (Airborne Remote Earth Sensing) aircraft. The Resurs-O1 remote sensing satellite, whose design was based on the successful Russian Meteor meteorological satellite series, was equipped with a range of remote sensing instruments and was roughly analogous to the American Landsat satellites. The WB-57F ARES was a modified RB-57F strategic reconnaissance aircraft (which itself was a modified B-57 Canberra tactical bomber) designed to carry up to 1,900 kilograms of remote sensing instruments at high altitudes. For our measurement campaign, ARES carried an imaging spectrometer capable of gathering data simultaneously in 75 spectral channels from 1.9 to 6.1 μm as well as a video camera with a 6.8° FOV to provide visible-band context images.

Comparison of a mosaic of ARES video images (top) with a Resurs-O1 MSU-E image (bottom) acquired over the area of Lamont, OK on July 27, 1995. Click on image to enlarge. (A.J. LePage/Visidyne)

The first opportunity to make observations as part of this effort occurred on July 27, 1995 in the vicinity of Lamont, Oklahoma which, in addition to being known for its afternoon thunderstorms, was also the site of the highly instrumented Southern Great Plains ARM (Atmospheric Radiation Measurement) site run by the US Department of Energy which could provide vital environmental support data. Near-simultaneous observations were successfully acquired using the MSU-E push-broom visible imager and from the red-near infrared channel of the MSU-SK conical scanner of the Resurs-O1 as well as the infrared spectral imager and video camera of the ARES aircraft. While the experiment was successful in that we had started to develop the means of working together with our Russian colleagues, no clouds were visible at the time of our observations.

A comparison of a panchromatic IR image swath taken by the ARES aircraft (top) and a false color image from the MSU-E push-broom scanner on Resurs-O1 (bottom) acquired on October 5, 1995 over California’s Sierra Nevada mountains. Mt. Whitney is near the center of the ARES image swath. Click on image to enlarge. (A.J. LePage/Visidyne)

The second joint observation opportunity during the 1995 campaign took place on October 5, 1995 this time in the vicinity of Mt. Whitney in California’s Sierra Nevada range. The Russian Resurs-01 satellite successfully acquired long wave infrared (LWIR) data using its MSU-SK conical scanner and visible data using its MSU-E push-broom imager. Likewise, the American ARES aircraft successfully acquired infrared spectral imaging and visible video data from three passes over Mt. Whitney – one pass looking at nadir and a pair of subsequent side-looking passes. But once again, while the objectives relating to cooperation with our Russian partners were met, there were no clouds present in the area as had been hoped. Nonetheless, I was able to use a sequence of video images acquired by ARES to create a three-dimensional reconstruction of Mt. Whitney as a demonstration of our early stereo algorithms then under development.

A 3D reconstruction of Mt. Whitney based on a stereo analysis of ARES video images acquired on October 5, 1995. Click on image to enlarge. (A.J. LePage/Visidyne)

The second near term experiment campaign took place in December of 1996 this time using Russian and American satellites.   Once again, the Russian Resurs-O1 satellite was employed working together with BMDO’s MSX (Midcourse Space Experiment) satellite. Because these two satellites were in near-polar, Sun-synchronous orbits with differing orientations, joint observations were only possible at high northern or southern latitudes where their orbits crossed. As luck would have it, both satellites nearly simultaneously passed over the vicinity of Mt. Erebus on Ross Island in Antarctica on December 23, 1996. While Resurs-O1 and MSX successfully carried out their observations, once again Mother Nature conspired against us and no clouds were visible in the area during the time of our experiment. Undeterred by the lack of clouds, I was able to combine data from the MSU-E push-broom imager of Resurs-O1 and the UVISI imager of MSX to create a three-dimensional reconstruction of Mt. Erebus as a further demonstration of our a stereo reconstruction algorithms.

Two views of a 3D reconstruction of Mt. Erebus in Antarctica based on a stereo analysis of visible-band images from Resurs-O1 and MSX acquired on December 23, 1996. Click on image to enlarge. (A.J. LePage/Visidyne)

In support of the conjunctive experiment with MSX, Resurs-O1 had also acquired LWIR data using its MSU-SK conical scanner in the area of Mt. Erebus on December 22, 1996 as a rehearsal of the following day’s joint observations and again on January 14, 1997 this time with plenty of clouds present. Unfortunately since neither MSX nor any other participating American spacecraft were in the area during these passes, stereo reconstructions of the clouds in these scenes was not possible. Likewise the BMDO-sponsored MSTI-3 (Miniature Sensor Technology Integration-3) satellite acquired an additional 444 images of the region at SWIR and MWIR wavelengths on March 2, 1997 as part of the campaign.

A false-color SWIR-MWIR mosaic of the area around Mt. Erebus constructed using images from MSTI-3 acquired on March 2, 1997. In this view, clouds and the open water are blue, bare ground is white and snow-covered areas are various shades of brown. Click on image to enlarge. (A.J. LePage/Visidyne)

The next phase of the near term experiments shifted from aircraft and satellite-based conjunctive experiments to a field measurement campaign designed to gather data in support of refining the RAMOS instrument requirements. For this phase, the FISTA (Flying Infrared Signatures Technology Aircraft) was employed to gather polarization measurements in the infrared in an effort to validate the models members of our science team were developing to predict the polarization properties of light reflected from water and ice clouds.

The FISTA aircraft (a modified USAF NKC-135E aerial refueling tanker) used for the RAMOS near term experiment campaigns in 1997, 1998 and 1999.

The FISTA aircraft (which was actually the second used in this long-running program) was a USAF NKC-135E aerial refueling tanker that had been modified in 1995 to act also as an instrument platform to gather data in support of various Defense Department research programs. For the 1997 campaign, FISTA was equipped with several instruments that had been modified to obtain polarization measurements at various infrared wavelengths. First was a trio of Michelson interferometers supplied by AFRL (Air Force Research Laboratory) to gather data in the 1.5 to 7.0 μm range of the infrared including the water absorption bands that were of the greatest interest to RAMOS. SAIRS (Schottky Array Infrared Sensor), also supplied by AFRL, was an infrared imager modified to obtain polarization images at wavelengths of 2.33 to 2.65 μm. Next was MAVIS (Multispectral Airborne Video Imaging System) built by Visidyne to obtain visible light context images and modified to provide polarization measurements for us. The last instrument was PEELS (Portable Eyesafe Environmental Lidar System), also built by Visidyne, to obtain information on the altitude of the clouds being observed by the other instruments as well as help determine whether they were composed of water or ice.

The first group of three flights took place in July of 1997 with another three flights taking place the following September. All together, about 16 hours of useful polarization data were gathered of cloud fields over various locations of the western US including observations of solar glints on clouds. These data largely agreed with our model results and allowed us to refine them further to provide better predictions of what would be observed from real clouds. Also noted was the wide variability of the scattering environment even in apparently featureless decks of clouds.

A comparison of visible band total intensity (left) and degree of polarization (right) images acquired by MAVIS during the September 18, 1997 FISTA flight. The dark smudge on the right side of the intensity image is an instrument artifact but note how this nearly featureless cloud deck shows a wide range of polarization. Click on image to enlarge. (A.J. LePage/Visidyne)

Building on our experience from our 1997 campaign with FISTA, we altered the mix of polarization instrumentation for a follow up campaign in 1998. Among the new instruments was HIP (Hyperspectral Imaging Polarimeter) built by SDL to gather infrared polarization data in the 2.5 to 3.5 μm spectral range. In addition, we also added the Aquameter Water Band Radiometer. The Aquameter was a scanning radiometer built by our Russian partners at the Vavilov State Optical Institute in St. Petersburg, Russsia that simultaneously gathered data in forward- and back-looking directions in four infrared bands from 4.6 to 7.2 μm . The purpose of this instrument was to gather pseudo-stereo imaging data in or near various water absorption bands to characterize the structure of clouds at pixel footprints of a few to a few tens of meters (depending on the altitude of the observed clouds relative to the FISTA aircraft) in order to help the science team refine the choice of filter bands to be used on the RAMOS IR imaging radiometer.

A comparison of Aquameter images in the 5.4 to 7.2 um band (top) and 4.6 to 4.9 um band (middle) with a cloud altitude trace derived from PEELS lidar data (bottom). These cloud data (with the cold clouds appearing dark against the warm atmosphere below) were acquired during the FISTA flight on October 1, 1998 (UT). Click on image to enlarge. (A.J. LePage/Visidyne)

A total of six flights were made in late September to early October 1998 over various locations in the southwestern US as well as off the Pacific Coast of California. The first three flights were dedicated primarily to obtaining polarization measurements in a continuation of our 1997 measurement campaign. The final three flights emphasized measurements using the Russian-built Aquameter. These six flights gathered a huge volume of data including around a dozen hours of Aquameter data that helped us further refine our models and the design requirements for the RAMOS instruments. One of the unexpected discoveries from our flights was the observation of tropospheric waves in the cloudless atmosphere in some of the Aquameter water-band images. While waves with scales on the order of ten kilometers had been observed by us and others in association with mountainous terrain and were orographic in origin, we had also recorded much smaller scale clear air waves with wavelengths on the order of a few hundred meters which had apparently never been observed before.

A calibrated Aquameter image acquired during the FISTA flight on September 30, 1998 (October 1 UT) in the 5.4 to 7.2 um water band that has been filtered and geometrically processed to correct for the instrument’s circular scan pattern. The observations of clear air waves with a scale length of a few hundred meters visible in this 15-km long image is considered unique. The faint, circular arcs visible in the image are instrument artifacts distorted by the processing. Click on image to enlarge. (A.J. LePage/Visidyne)

A final FISTA measurement campaign in support of RAMOS was flown in December 1999. These flights used essentially the same mix of instruments flown in 1998 with some modifications made to improve instrument performance. While three of these flights had the Aquameter operating in a nadir-viewing mode as had been done during the 1998 campaign, for the remaining three flights, the center of the Aquameter’s scan pattern was canted forward to provide imaging data at higher nadir angles in support of RAMOS science objectives. Once again, all six flights were successful in gathering huge amounts of additional polarization and IR radiance data including over 18 hours of useful Aquameter data. With these data in hand, the near term experiments of the RAMOS program were ended.

Bibliography

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