During the past several decades, space radiocommunications have greatly expanded the scientific and telecommunications capabilities of our nation and world. The space services today provide communications between fixed and mobile users on the Earth, much as do the terrestrial fixed and mobile services. They provide communications to allow spaceborne platforms to disseminate information to, and collect information from, the Earth's surface. They also provide the ability to look outward into space, and back toward the Earth from space, to further our scientific knowledge.
Many of the space services are closely related to terrestrial services. For example, the mobile- and fixed-satellite services are similar to the terrestrial mobile and fixed services and often compete in the same markets. For this reason, they, along with the broadcasting-, radiodetermination-, amateur-, and standard frequency and time signal-satellite services are discussed in the same chapters as the corresponding terrestrial services.[EN479]
This chapter discusses spectrum requirements for space services not included in the above list, mainly because they do not have closely related terrestrial counterparts. These include the inter-satellite service and the proposed general-satellite service, which are related to satellite communications; the space operation service; and the services related to space sciences. The latter group includes the space research service, the earth exploration-satellite service, and the meteorological-satellite service. While they do not involve space services, radio astronomy and radar astronomy are covered in this chapter because they are space sciences.
Satellite Communications Services
A major function of the space services is to provide communications between widely separated points on the Earth. While the bulk of these communications fall to the mobile-, fixed-, and broadcasting-satellite services, two other services may see significant use in the future. The inter-satellite service provides communications between satellites. If established, the general-satellite service would combine the functions of several existing satellite services, providing greater flexibility for multi-function systems.
Although most satellite communications involves links between satellites and the Earth, satellites and other spacecraft must often communicate among themselves. Communications links that involve more than one satellite require inter-satellite links. Non-geostationary U.S. satellites and other spacecraft in low Earth orbit generally relay their signals to the ground through geostationary data relay satellites. Manned space missions involving multiple spacecraft or extra-vehicular activities also require "inter-satellite" radiocommunications links.
While the inter-satellite service can support these communications links,[EN480] they are usually accommodated in other services. Data relay satellites, which serve satellites and spacecraft in low-Earth orbit, operate in the space research, space operation, and earth exploration-satellite services. They will, however, use inter-satellite service allocations in the future. The fixed-satellite service can accommodate links between satellites operating in that service.[EN481]
The Tracking and Data Relay Satellite System (TDRSS) provides communications between low Earth orbit satellites and Earth. TDRSS uses the 2025-2110 MHz and 2200-2300 MHz bands and the 13.4-14 GHz and 14.5-15.35 GHz bands, all allocated to the space research service. The proposed Advanced TDRSS (ATDRSS) system will use frequencies in the inter-satellite service near 23 GHz as well as those in the space research and fixed-satellite (for feeder links) services.
Non-GSO satellites in the mobile-satellite service could be major users of inter-satellite links in the future. Systems operating above 1 GHz may require inter-satellite links in addition to planned feeder links.[EN482] Plans for the Iridium system, for example, call for inter-satellite links in the 22.55-23.55 GHz band. Under an agreement with NASA, the FCC will accommodate future inter-satellite links for mobile-satellite systems in the 24.45-24.75 GHz band, which was designated for such systems at WARC-92.[EN483]
Inter-satellite links are unique in that they do not involve propagation through the Earth's atmosphere. Therefore, the atmospheric properties that preclude communications between the Earth and space at many frequencies above 10 GHz benefit the inter-satellite service in that they allow communications effectively insulated from terrestrial interference. Extending this reasoning, DOD remarked in its comments that laser communications would be ideal for inter-satellite links.[EN484]
Spectrum Requirements for the Inter-Satellite Service
Those who commented on the inter-satellite service expressed a belief that allocations are generally adequate.[EN485] Although NASA requested, however, that the 22.55-23.55 GHz band be extended to 23.6 GHz, NTIA must first address the sharing potential between the inter-satellite service and the other services allocated in this band.[EN486]
Despite the advantages of using higher frequencies for inter-satellite links, NASA contends that lower frequencies are required for communications with an omni-directional antenna if a satellite becomes unstable. Because of these requirements, NASA says the 2025-2110 MHz and 2200-2290 MHz bands will be needed indefinitely for inter-satellite communications in the space research service. NASA believes, however, that these bands must not be allocated to the inter-satellite service, because the defined uses would be too broad.[EN487]
At WARC-92, the United States proposed the creation of a new radiocommunication service to accommodate multi-function satellite systems, specifically those combining fixed, mobile and point-to-multipoint functions.[EN488] Under the proposal, the primary fixed-satellite service and secondary mobile-satellite service allocations in the 19.7-20.2 GHz (space-to-Earth) and 29.5-30.0 GHz (Earth-to-space) bands would have been replaced by primary general-satellite service allocations.[EN489]
WARC-92 did not establish a general-satellite service. Instead, it upgraded the mobile-satellite service allocations to primary status in the 20.1-20.2 GHz and 29.9-30 GHz bands and to primary status in Region 2 only in the 19.7-20.1 GHz and 29.5-29.9 GHz bands. The mobile-satellite service allocations remained secondary in the latter bands in Regions 1 and 3.[EN490] A new footnote to the ITU frequency allocation table recognizes "networks which are both in the fixed-satellite service and in the mobile-satellite service" as including point-to-point and point-to-multipoint links between fixed and mobile earth stations.[EN491] The conference recommended further study of the general-satellite service concept as well as its inclusion on the agenda of the next competent WARC.[EN492]
Though the establishment of this service may raise a sharing issue nationally between the various satellite services, and internationally between the proposed service and the fixed and mobile services in the 19.7-20.2 GHz band, it does not involve a requirement for any additional spectrum in the near future.
Space Operation Service
In addition to the communications related to the spacecraft's mission, satellites and other spacecraft also require communications specifically for their operation. These functions include receiving commands from the ground and replying with information on the spacecraft's condition. NTIA defines the space operation service as "[a] radiocommunication service concerned exclusively with the operation of spacecraft, in particular space tracking, space telemetry and space telecommand."[EN493] These operations are called TT&C.[EN494]
Different TT&C communications are required for the various phases of a spacecraft's mission. This section describes both long-term, in-orbit TT&C and the short-term TT&C communications required for launch, satellite positioning, and spacecraft reentry.
TT&C communications for a spacecraft normally occur in the same frequency band used by the spacecraft for communications related to its mission.[EN495] For example, spacecraft operating in the fixed-satellite service will generally multiplex the TT&C with the communications in fixed-satellite service bands. This practice results in considerable cost savings and improved reliability as the same equipment, including redundant systems, can be used for both functions.[EN496]
In some cases, however, TT&C links in a separate band are necessary. NASA's data relay satellites, although they combine TT&C with the feeder links, require backup TT&C links at 2 GHz. The 2 GHz backup links are crucial because they provide all-weather communications to an omni-directional satellite antenna. These TT&C links also allow direct communications between LEO satellites and earth stations for emergencies and contingencies.[EN497]
WARC-92 allocated the 2025-2110 MHz (Earth-to-space and space-to-space) and 2200-2290 MHz (space-to-Earth and space-to-space) bands to the space research, space operation, and earth-exploration satellite services on a primary basis.[EN498] NTIA adopted the new allocations for Federal Government use in the 2200-2290 MHz band in the National Table of Frequency Allocations. Federal use of the 2025-2110 MHz band continues under footnote allocations.[EN499]
Despite the desire that the 2 GHz allocations be upgraded to primary status in the National Table of Frequency Allocations,[EN500] commenters did not indicate the need for new allocations for in-orbit TT&C.
Various types of launch vehicles are used to deliver payloads into space. The original and most common is the multi-stage expendable launch vehicle, which is still used to orbit many payloads. In the early 1980's, the United States began launching the Space Transportation System or "Space Shuttle," which could carry a crew and be used for repeated flights. More recently, the Pegasus launch vehicle, released from an aircraft at high altitude instead of being launched from the ground, introduced economical dedicated launches of small payloads.[EN501] Development continues on a variety of suborbital, orbital, reentry, and reusable single-stage-to-orbit (SSTO) vehicles to support both Federal and commercial operations.[EN502]
TT&C requirements during launch, satellite positioning, and reentry (if applicable) are very different from those for in-orbit spacecraft. During launch, a radar system is needed to determine the position of the spacecraft. A flight termination command system is necessary if a launch vehicle must be destroyed. Third, telemetry is needed to determine the condition of the spacecraft. Communications required during satellite positioning are much like in-orbit TT&C except that they are needed for a relatively short time. Manned spacecraft have additional communications requirements, including voice and video channels.[EN503] Aeronautical communications, in addition to telemetry and position determination, are critical for reusable vehicles, because the reentry phase includes flight within the atmosphere. The precision of position determination has significant impact on the landing accuracy of ballistically reentering vehicles. For example, an uncertainty of one mile in altitude could cause the vehicle to miss the landing site by ten miles.[EN504]
Federal Government Launch Facilities
NASA and the Air Force launch government payloads, including military satellites, weather satellites, data relay satellites, and scientific payloads, among others. NASA and the Air Force have launch sites at several locations in the U.S. and tracking stations worldwide. In its comments, NASA indicated that allocations for government launch telemetry, radar tracking, and flight termination are adequate.[EN505]
Commercial Launch Facilities
Communication satellites dominate in the total number of commercial satellites launched in the past decade. Navigational satellite constellations, particularly in the United States, represent a rapidly growing use of new satellite technology. Small size payloads in low-Earth orbit, designed for data messaging and location service, are another example of new satellite technology meeting the needs of the commercial sector. While communications satellites are the most profitable of the commercial satellites, significant efforts are devoted to establishing new commercial satellite uses such as microgravity and remote sensing.[EN506]
Until the mid 1980's, NASA provided launch services for both government and commercial payloads. Since 1990, however, commercial payloads have greatly relied on commercial launch vehicles.[EN507] Although current launch vehicles utilize Federal Government launch sites and tracking stations, the private sector has begun to develop plans for new commercial launch sites. States such as Florida, Alaska, New Mexico and California recently received Federal funding to examine the feasibility of developing commercial spaceport facilities. For example, over the past several years, Hawaiian state officials have worked with the Department of Transportation's Office of Commercial Space Transportation (OCST) to address issues pertinent to spaceport development. Sites such as these will still have to support launch vehicle communication requirements that have long been associated with federal sites.[EN508]
To accommodate the telemetry requirements of commercial launch vehicles, the FCC and NTIA allocated six frequencies in the 2310-2390 MHz band.[EN509] WARC-92, however, reallocated the 2310-2360 MHz band for satellite sound broadcasting in the United States and India, essentially reducing the number of commercial launch telemetry frequencies in the United States from six to three.[EN510]
OCST sees a growing need for communications for commercial launch vehicles. According to OCST, "the industry is now evolving toward new vehicles, toward reentry vehicles that have a whole host of additional spectrum requirements, and toward commercial spaceports"[EN511] If the demand for commercial launches is sufficient, spaceports or possibly even commercial airports could be used for launch and reentry of certain vehicles. Communications requirements, and thus spectrum requirements, for these developments have yet to be determined.[EN512]
According to OCST, the allocations for commercial launch telemetry seem to be adequate for the present. However, they have expressed concern that "there may not be adequate frequency allocations in the longer term . . . to support the needs of a growing industry."[EN513] At issue is the impact the WARC-92 reallocation will have on the range operations of commercial space launches. Further, it is not fully clear what effects the limited number of frequencies will have on the industry.[EN514]
OCST has taken the initial steps to address the issue of frequency allocation for commercial launches. OCST maintains that the size of the late 1990's commercial user base will consist of an average annual launch rate of 8 (compared to 14 and 17 for NASA and DOD, respectively). Efforts to model long-term commercial launch rates is one of many approaches OCST plans to employ to aid in determining spectrum requirements. The concern still remains, however, that the available spectrum may be inadequate for requirements beyond the next decade. If the commercial launch industry does experience tremendous growth, the available frequencies could soon prove insufficient for its needs.[EN515]
Services Related to Space Sciences
The final space services discussed are those related to space sciences.[EN516] Included are the space research, earth-exploration satellite and meteorological-satellite services. The remote sensing aspects of these services are discussed in a separate section. Radio astronomy and radar astronomy, although they are terrestrial functions, are also included because of their similarities with the space services.
Initially, the U.S. space program was a scientific program run by the Federal Government. However, many activities once classified as research have commercial applications, such as biochemical crystallizations and lunar mining for fusionable materials. NASA contends that U.S. commercial space development at 2 GHz is disadvantaged compared to that of other countries because of a lack of allocations for commercial activities. NASA believes the space science bands should be shared between Federal and non-Federal users.[EN517]
NTIA defines the space research service as "[a] radiocommunication service in which spacecraft or other objects in space are used for scientific or technological research purposes."[EN518] The space research service includes Earth-to-space and space-to-Earth links, both near-Earth and deep space,[EN519] space-to-space links, and active and passive remote sensing.
Because most of its space activities are research-oriented, NASA has historically used the space research service for the bulk of its radiocommunications. However, NASA now believes that it should be using other radio services since many of its research activities lead directly to commercial activities. The experimental connotation of the space research service is no longer applicable to much of NASA's work. Further, NASA believes that space research bands should be allocated for both Federal and non-Federal users.[EN520]
NASA believes that current allocations for the space research service (not including active and passive remote sensing) are generally adequate in location and bandwidth. However, the status of some allocations may be inadequate.[EN521] NASA's concerns regarding several frequency bands allocated to the space research service are discussed here.
WARC-92 allocated the 410-420 MHz band to the space research service on a secondary basis for space-to-space links within five kilometers of an orbiting, manned space vehicle.[EN522] The United States has adopted the secondary allocation for use by Federal Agencies.[EN523] Potential U.S. uses of this allocation include the Space Station Freedom and the Space Shuttle. NASA, however, wants the allocation to have primary status.[EN524]
Some of NASA's concerns about the 2025-2110 MHz and 2200-2290 MHz bands were discussed earlier in conjunction with the inter-satellite service.[EN525] NASA believes the U.S. space program needs to maintain access to the 2 GHz space research bands because of their all-weather capability, because they allow the use of omnidirectional antennas that provide contingency communications for unstable satellites, and because planned data relay satellites will use the 2 GHz band indefinitely.[EN526]
Deep space communications for U.S. satellites are provided at 2110-2120 MHz (Earth-to-space) and at 2290-2300 MHz (space-to-Earth). NASA states that keeping deep space frequencies free from interference is critical because much of the data obtained from deep space probes is based on measurements that are not repeatable and because the frequencies will be used in the future for manned deep space missions.[EN527] WARC-92 allocated the 2110-2120 MHz band to the space research service internationally on a primary basis for deep space Earth-to-space links.[EN528] NASA believes the National Table of Frequency Allocations should contain this allocation for both Federal and non-Federal users.[EN529]
The 12.75-13.25 GHz and 16.6-17.1 GHz frequency bands are also allocated to the space research service for deep space Earth-to-space links.[EN530] NASA wants these allocations to not be limited to deep space communications.[EN531]
Systems operating in the earth exploration-satellite service are used to obtain "information relating to the characteristics of the Earth and its natural phenomena . . . from active sensors or passive sensors on earth satellites."[EN532] The service is also used to collect similar information from terrestrial or airborne platforms, to interrogate platforms, and to relay the information collected to earth stations. Like the space research service, the earth exploration-satellite service includes Earth-to-space, space-to-Earth, and space-to-space links as well as active and passive remote sensing. While the sensors in the space research service are directed into space, those in the earth exploration-satellite service are directed toward the Earth. Again, the remote sensing applications of the service are discussed later in this chapter.
According to NASA, the current number and location of allocations are generally adequate.[EN533] Concerns about remote sensing are discussed below. Concerns about links near 2 GHz were discussed earlier.[EN534]
The meteorological-satellite service is "[a]n earth exploration-satellite service for meteorological purposes."[EN535] The service is used to support weather satellites operated by NOAA and DOD. Most of the allocations are used to send meteorological data from geostationary and polar-orbiting satellites to earth stations. A few of the allocations, however, are used for Earth-to-space links.[EN536]
Commenters believe that, for the present, allocations for the meteorological-satellite service are adequate.[EN537] However, NOAA believes that increased data rate requirements from polar satellites will make about 100 MHz of additional spectrum necessary.[EN538] We believe these requirements can be accommodated in existing frequency bands at 7 and 8 GHz.[EN539]
Active and passive remote sensing make up a significant portion of the activities in the space research and earth exploration-satellite services.[EN540] In the space research service, active sensors are used to measure such things as solar winds and lunar soil content while passive sensors are used for Very Long Baseline Interferometry (VLBI) in bands also allocated to the radio astronomy service. In the earth exploration-satellite service, remote sensing devices are directed toward the Earth instead of into space.[EN541]
Commenters expect an increase in the use of remote sensing from satellites because of increasing environmental concerns.[EN542] While this does not necessarily translate into a requirement for new allocations, NASA would like to see some secondary allocations upgraded to primary status as well as certain other changes. The desired changes for specific frequency bands are discussed below.[EN543]
At one time, NASA thought it was appropriate to allocate the same frequency bands for both the space research and earth exploration-satellite services. Now, however, NASA believes it may be more appropriate to have separate bands for earth sensing and space sensing from satellites.[EN544] NASA believes that allocation of the same bands for the space research and earth exploration-satellite services may be inappropriate and confusing to users and regulators. NASA therefore favors deleting some space research service allocations in bands to which the earth exploration-satellite service is also allocated.[EN545] In some cases, more study is needed to determine which allocations should be deleted.[EN546] As with some other space services, NASA believes frequency bands allocated for remote sensing should be shared by Federal and non-Federal users.[EN547]
Under International Footnote 713, the 1215-1300 MHz, 3100-3300 MHz, 5250-5350 MHz, 9500-9800 MHz, and 13.4-14 GHz radiolocation bands may also be used in the space research and earth exploration-satellite services for radiolocation (active sensors) on a secondary basis.[EN548] The 17.2-17.3 GHz radiolocation band is also allocated to the space research and earth exploration-satellite services for active sensors on a secondary basis.[EN549] NASA requests that these bands be available for active sensors on a primary basis.[EN550]
The 13.25-13.40 GHz band is allocated, nationally and internationally, to aeronautical radionavigation for Doppler navigation aids. The band is also allocated, on a secondary basis, to the space research service for Earth-to-space links.[EN551] Instead of the secondary allocation to the space research service, NASA favors a primary allocation to the earth exploration-satellite service for active sensors.[EN552] The 24.05-24.25 GHz radiolocation band has a secondary allocation to the earth exploration-satellite service for active sensors.[EN553] NASA requests that this allocation be raised to primary status.[EN554]
Two additional radiocommunications functions are included in this chapter. Radio astronomy and radar astronomy, while they are terrestrial rather than space systems, have many similarities with space systems. They are the terrestrial counterparts of the active and passive remote sensing accommodated in the space research service. The users of radio astronomy and radar astronomy are also the users of the space services.
Some radio astronomy observations are currently being made at frequencies beyond the 300 GHz upper limit of the U.S. allocation tables. In fact, radio astronomers have identified spectral lines of great importance at frequencies beyond 800 GHz.[EN555] Simultaneously, research and development continues on active systems such as radiolocation devices that also use frequencies above 300 GHz.[EN556] To minimize the potential for interference to radio astronomical observations by active devices at frequencies above 300 GHz, the National Science Foundation believes the extension of the allocation tables beyond the current limit should be considered.[EN557]
NTIA defines radio astronomy as "[a]stronomy based on the reception of radio waves of cosmic origin."[EN558] The service is unique in that it involves only passive systems. Since the signals received emanate from natural sources, the radio astronomers have no control over the power, the frequency, or other characteristics of the emissions. Radio astronomers employ radio telescopes, highly sensitive receivers with large, high-gain antennas, to pick up the weak signals from space.
Because the desired signals are so weak and the receivers are so sensitive, radio telescopes are highly susceptible to interference.[EN559] Radio observatories are usually built in remote locations with surrounding terrain that provides natural shielding from interference sources. Nonetheless, effective spectrum management is critical to protect the radio telescopes from harmful interference. Major sources of interference are spurious, harmonic, and adjacent band emissions from satellites, large numbers of nonlicensed devices, and ultrawideband devices.[EN560]
Radio astronomers are interested in two distinct types of cosmic signals: wideband continuum emissions and narrowband spectral line emissions. Continuum emissions, both thermal and non-thermal, extend continuously over most of the radio frequency spectrum.[EN561] Thermal emissions generally increase in intensity with increasing frequency, while the intensity of non-thermal emissions generally decreases with increasing frequency.
Spectral line emissions result from changes in the energy states of individual cosmic atoms and molecules.[EN562] Spectrum planning for observation of these emissions is difficult because the Doppler effect causes a shift of the apparent frequency of the emissions as a function of the relative velocity of the source.[EN563]
Spectrum Requirements for Radio Astronomy
Radio astronomers have no control over the signals they are receiving. The spectrum requirements for radio astronomy are therefore based on physical phenomena rather than expected growth, as is the case for most other services.
Using terrestrial radio telescopes, radio astronomers can observe cosmic phenomena at frequencies ranging from 15 MHz to over 800 GHz.[EN564] To meet the needs of radio astronomy, frequencies at regular intervals across this range must be protected from interference in the vicinity of the radio observatories. The basic plan of spectrum management for radio astronomy is to protect small bands across the range for continuum observations, while choosing those bands so they contain the spectral lines of greatest interest.
Ideally, allocations with a bandwidth equal to five percent of the center frequency would be available at one octave intervals above 1 MHz for continuum observations. Minimally, the bandwidth of the allocations should be one percent of the center frequency. Between 1 MHz and 1 GHz, the allocations should be spaced every half-octave.[EN565]
The National Science Foundation expressed concern that it had no protected frequencies for observations between 74.6 MHz and 406.1 MHz. They suggest radio astronomy allocations in the bands shown in Table 5-1 to remedy this problem.[EN566] The total spectrum involved is 9.55 MHz.
Frequency Band Bandwidth ______________ _________ 150.05-153 MHz 2.95 MHz 322-328.6 MHz 6.6 MHz ____ Total Spectrum Requested: 9.55 MHz
Several other radio astronomy bands have less than the min imum one percent bandwidth. NSF recommends increasing the bandwidths of the eight frequency bands shown in Table 5-2.[EN567] The total spectrum required to increase these ban dwidths is about 169 MHz.
Astronomers have identified over 550 spectral lines. The Int ernational Astronomical Union maintains a list of the fre quencies it considers most important for spectral line observations.[EN568] The frequency bands listed in Table 5-3 are those identified by the National Science Foundation as necessary to extend protection of the most important spectral lines to more highly redshifted (lower) frequencies or to afford protection to important spectral lines that are not currently within a band allocated exclusively to passive services.[EN569] The total additional spectrum requested in these bands is 62.3 MHz.
Frequency Current One Percent Additional Spectrum Band Bandwidth Bandwidth Requested ____________ _________ ________ __________________ 13.36-13.41 MHz 50 kHz 134 kHz 84 kHz 25.55-25.67 MHz 120 kHz 256 kHz 136 kHz 406.1-410 MHz 3.9 MHz 4.1 MHz 200 kHz 608-614 MHz 6.0 MHz 6.1 MHz 100 kHz 2690-2700 MHz 10 MHz 27 MHz 17 MHz 4990-5000 MHz 10 MHz 50 MHz 40 MHz 10.6-10.7 GHz 100 MHz 107 MHz 7 MHz 15.35-15.4 GHz 50 MHz 154 MHz 104 MHz ____ Total Spectrum Requested: 169 MHz
Above 20 GHz, radio astronomy allocations are still adequate, since this spectrum is not in as great demand and subject to the same allocation pressures as spectrum below 20 GHz. Preservation of these allocations is important to the radio astronomers.[EN570]
The total of the spectrum requirements shown in the three tables is about 241 MHz. Spectrum requirements for radio astronomy are somewhat different from those of most other services in that they are not dictated by predicted traffic requirements and, in the case of spectral lines, involve very specific frequencies. Spectrum requirements are 9.6 MHz of additional allocations, and access to an additional 231 MHz by local coordination.
Additional Allocation Bandwidth of Allocation 1370-1400 MHz 30 MHz 1606.8-1610.6 MHz 3.8 MHz 1659.8-1660 MHz 200 kHz 1714.8-1722.2 MHz 7.4 MHz 4813.6-4834.5 MHz 20.9 MHz ____ Total Spectrum Requested: 62.3 MHz
Unlike radio astronomy, radar astronomy involves transmission of radio signals as well as reception. Radar astronomy does not have its own service. Instead, it is conducted in radiolocation bands, in cooperation with other users of the bands.
The NASA radar at Goldstone, California is used for locating and examining celestial bodies such as planets, moons, and asteroids. The data obtained is used, among other things, for the determination of landing site locations for interplanetary spacecraft. The radar operates in radiolocation bands at 2320 MHz and 8510 MHz. The sensitivity of the receiver is the same as that for the deep space network.[EN571] The National Science Foundation's radio telescope at Arecibo, Puerto Rico includes a radar operating at 2380 MHz. This radar is used for activities such as planetary mapping and imaging, investigation of asteroids, and tracking of space debris. NSF coordinates the operation of this radar with military users of the frequency band.[EN572]
According to commenters, spectrum requirements for radar astronomy are adequately met at the present time, and "it is expected that they will be accommodated with relatively little effort in the foreseeable future." [EN573]
Requirements for new and expanded frequency bands for radio astronomy total approximately 240 MHz. These requirements represent the top priorities for radio astronomers, who seek additional spectrum to better study cosmic phenomena. Allocation changes for any of these frequency bands will probably involve sharing arrangements as opposed to relocating existing users.
Although they represent a wide variety of systems and expect vigorous growth, the space services discussed in this chapter had few significant requirements for additional frequency spectrum. Those mentioned include:
Some of these requirements, such as those for the inter-satellite service and for remote sensing, may be satisfied through spectrum sharing with minimal impact on existing users of the bands.