We present the concept of a reusable science probe based at the International Space Station (ISS). A wide range of unique scientific and technical investigations will be enabled through the large aperture and high mass capabilities of the platform. The ISS infrastructure is used for servicing the spacecraft and/or scientific instrument, as well as upgrading the scientific payload. During the data gathering phase, envisioned to last six months to two years, the spacecraft will be a free-flyer in the ISS orbit, avoiding operational constraints imposed by the ISS environment and allowing full control of the experiment by the investigation team. Periodic docking with the ISS provides the servicing capability. A limited spare parts cache can be provided by the ISS “mother ship” using excess STS payload capacity to this frequent-flyer destination. By eliminating the need for mission-unique spacecraft and operations infrastructure for a wide range of missions, a tremendous return on investment can be realized

Cheng, Edward S.

English

Embry-Riddle Aeronautical University

The Space Congress® Proceedings 1996 (33rd) America's Space Program -What's Ahead? Apr 24th, 2:00 PM - 5:00 PM Paper Session II-A - Free-Flying Platforms for the International Space Station: Large Aperture Science at Medium-Explorer Cost Edward S. Cheng NASA/ Goddard Space Flight Center Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Cheng, Edward S., "Paper Session II-A - Free-Flying Platforms for the International Space Station: Large Aperture Science at Medium-Explorer Cost" (1996). The Space Congress® Proceedings. 9. https://commons.erau.edu/space-congress-proceedings/proceedings-1996-33rd/april-24-1996/9 This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact commons@erau.edu. F R E E- FL Y I N G  P L A T F O R M S  F O R  T H E  I N T E R N A T I O N A L  S P A C E  S T A T I O N:L A R G E  A P E R T U R E  S C I E N C E  A T  M E D I U M- EX P L O R E R  C O S TEdward S. ChengNASA/Goddard Space Flight Center, Code 685Laboratory for Astronomy and Solar PhysicsGreenbelt, MD 20771301-286-5038ec@cobi .gs fc .nasa .govA B S T R A C TIWe present the concept of a reusable science probe based at the International SpaceStation (ISS). A wide range of unique scientific and technical investigations will beenabled through the large aperture and high mass capabilities of the platform. TheISS infrastructure is used for servicing the spacecraft and/or scientific instrument, aswell as upgrading the scientific payload. During the data gathering phase, envisionedto last six months to two years, the spacecraft will be a free-flyer in the ISS orbit,avoiding operational constraints imposed by the ISS environment and allowing fullcontrol of the experiment by the investigation team. Periodic docking with the ISSprovides the servicing capability. A limited spare parts cache can be provided by theISS “mother ship” using excess STS payload capacity to this frequent-flyer destination.By eliminating the need for mission-unique spacecraft and operations infrastructurefor a wide range of missions, a tremendous return on investment can be realized.oritsI N T R O D U C T I O NMany forefront scientific questions now require the use of large aperture instrumentshigh mass payload capability. The aperture of an instrument is directly related toresolving power for imaging. In the newly developing far-infrared and submillimeterwavelength regimes, a significant improvement in resolution has a dramatic impact onscientific discovery potential. For missions that require mass for improving interactionprobability (as in high energy particle experiments), an increase in mass is directly relatedto an increase in sensitivity. Such payload capabilities are not readily available with typicalMedium-Explorer (MIDEX) launch vehicles, but could be within or below the programcost guidelines.At the same time, the capabilities of an extensive range of previously used flighthardware are not fully exploited by current or planned missions, The development costfor this hardware can be applied to future missions, eliminating the need for developingmission-specific spacecraft for those missions where existing hardware is a good fit. (Thiswould apply equally to low-cost new designs for reusable spacecraft. )This hardware could be used in an aggressive, austere, and flexible program thatsupports a series of forefront scientific and technical investigations. The ISS infrastructurewill help to achieve the full return from such a program by enabling an active maintenanceand instrument upgrade plan.4-28T H E  B A S E L I N E  P R O G R A MThe fundamental idea is simple. A platform, regarded as a piece of ISS infrastructure,is a common spacecraft for a sequence of missions that can accommodate a wide rangeof scientific and technical disciplines. This platform is launched into, and maintained atan ISS compatible orbit, and has the capability of redocking with the ISS for servicingoperations. Previous studies of a generic Station Keeping Platform (SKP) have shownthat such a platform can be sent away and retrieved using only a modest amount ofpropulsion.A sequence of scientific and technical payloads are then brought to the ISS. ISS ser-vicing replaces the payload section of the spacecraft, creating a new configuration forthe next mission. The mission duration can be specific to the needs of the particularpayload, and defines the time that the free-flyer is independent of the ISS. We anticipatethat for most missions, this time ranges from roughly six months to two years. Duringthe mission, it operates as an independent spacecraft, allowing for low-cost, simplifiedscience operations using standard infrastructure for the program. For example, there isthe proven, low-cost flight operations model through the EUVE Innovative TechnologyProgram (University of California, Berkeley).The ISS infrastructure is also used for maintaining the spacecraft. When docked, anyneeded repair and replacement of spacecraft Orbital Replacement Units (ORUs) can beexecuted (e.g., transponders, batteries, etc. ). Many small ORUs and instrument partscan be brought up using excess STS capacity to the ISS and then stored at the ISS forlater use. Scientific payload servicing (e.g., cryogenic recharge using SHOOT technology)can also take place, in which case the “next” mission is a renewed version of the previousone.Note that the uplift capability can be provided by either STS or expendable launchvehicles. This is a detail that depends on the payload requirements and availability oflaunch vehicles. There is nothing intrinsic in this program that requires the STS to launchall of the components. However, it can make effective use of any excess STS capacity.The programmatic advantages of such a program are significant. By developing a rangeof low-cost instruments, the risks associated with any one instrument are spread acrossthe entire program. Extraordinarily capable scientific instruments also result from thehigher risk that is acceptable because the instrument is retrievable. By using a standardset of ground test and validation equipment (simulators, tooling, etc.), life-cycle cost forthe program is minimized. In addition, the well-defined and tested interfaces on thespacecraft will minimize the cost of integration and testing.This “science probe” concept will capture public imagination as a prototype for futuremodes of exploration from a “mother-ship. ” It is a capability that will be routinelyrequired as we expand beyond the low Earth orbit environment.T H E  A D V A N T A G E  F O R  S C I E N C E  A N D  T E C H N O L O G Y  M I S S I O N SIn addition to supporting missions that cannot fit within the technical profiles ofcurrent programs, such a program can provide other significant advantages as well.First, it could enable a range of fast-turnaround missions by allowing a larger fractionof resources to be allocated to instrument development by eliminating spacecraft develop-4-29ment. A highly capable platform will provide relief from weight and volume constraints,potentially lowering cost or easing schedule because the fundamental components do notall have to be exquisitely engineered. By providing this fast-turnaround mode, it en-ables “proof-of-concept” missions for testing technology and mitigating risk for the largestand most ambitious missions. The scientific community can also use this capability formissions-of-opportunity in the ISS era.Secondly, the program is ecologically sound. Highly capable hardware is reused toleverage past investments into future exploration. This happens naturally with the space-craft hardware, but the scientific hardware will also be retrieved and the investmentprotected. In an era where we are accomplishing ambitious programs in multiple phases,such a capability could reduce overall cost to a long-term investigation.A M O D E L  S O L U T I O N , T H E  a S C I E N C E  P R O B EAs an example of an implementation of this program, there has been an informal studyof reusing the Explorer Platform (EP, currently used by the Extreme Ultraviolet Explorer,EUVE) as the spacecraft. In this new configuration, dubbed the Alpha Science Probe, allof the requirements of the baseline program can be met. The sequence of events requiredare listed below.• Retrieve the hardware using an STS flight to the 28°.8 inclination orbit of EUVE.• Immediately upon return, execute a ground-based refurbishment of the EP space-craft. The current state of the hardware requires only minimal work: replacing afailed transponder, tape recorder, and batteries. The addition of a modular propul-sion unit is needed to enable the docking and free-flying activities.• Mate the spacecraft with the first scientific payload that has been developed andtested using existing GSE, tooling and simulators.• Prelaunch into ISS orbit and perform the first a S P scientific mission,• When ISS is ready for servicing operations (in the 2002 time-frame), dock with ISSand execute the follow-on phases of the program.This hardware is a good example of what is needed for the program. Almost all ofthe EP hardware is reused, including GSE and other infrastructure. Together with thetested electrical and mechanical interfaces, this makes the scientific instrument integra-tion a low-risk operation. The platform is modular, and has been designed from the startto support astronaut Extravehicular Activities (EVA) for servicing. Thus, on-orbit refur-bishment of the spacecraft is a part of the original intent, and is not only feasible butalready accounted for in the design. Furthermore, the scientific payload interface is EVAcompatible, remotely commendable, and intended to be used on-orbit.The technical capabilities of the platform are summarized in Table 1. Clearly, it has theinfrastructure to support even the most ambitious of scientific payloads, and demonstratesmany desirable features of a versatile platform.The study also shows that, based on the performance of other spacecraft of almostidentical design, a significant part of its useful life still remains (at least 10 years). This life4-30Table 1: a S P Top-Level SpecificationsCategory Item ValueGeneral Payload WeightDiameterOrbitLifeServicingPowerAttitude Control TypeRatesPointingCommunications Telemetry(upgradable) Payload DataCommandsUp to 5,000 kg (STS)up to 4 m, launch vehicle limitedISS co-orbiting (~ 230 nm)51°.6 inclination> 10 years with servicing6 to 12 month intervals300 W continuous, 1 KW maximum3-axis stabilized, zero-momentum,stellar reference2°/sec maximum slewHigh rate: 0°.5/sec for 5000 slug-ft2Low rate: 0°.1/sec for 5000 slug-ft2Stability: 10 arcsec (3 s)32 Kbps prime, 1 Kbps backupup to 26 Kbps scienceup to 512 Kbps direct downlink1 Kbps prime (TDRSS)2 Kbps backup (DSN)125 bps backup (TDRSS)is ensured by the availability of servicing operations. This orbital experience also indicatesthat the maintenance cost of the spacecraft will be small (~ $10M per science “mission”cycle). The initial refurbishment cost (less than ~ $10M) is also minimal compared tothe development cost of the spacecraft and supporting equipment (~ $100M). Thus, avery large return can be realized.T H E  P R O C E S S  F O R  D E F I N I N G  T H I S  P R O G R A MRecognizing the potential benefits of this program to a large scientific and technicalcommunity, the NASA Research Management Office (RMO) at the Johnson Space Centerin Houston, Texas, in cooperation with NASA Headquarters Offices of Space Science,Mission to Planet Earth, Life and Microgravity Sciences, and Applications, Space Accessand Technology, together with the Goddard Space Flight Center is sponsoring a workshopon May 14 and 15, 1996 to explore the scientific and technical logic of a free-flyer scienceprogram for the ISS. The main goals will be to assess the utility of such a programto the community, and evaluate possible implementation concepts. The purpose of the4-31workshop is not to officially solicit proposals for possible funding, but rather to identifygeneric, functional uses of such a system from a broad range of users. This workshop willbe co-hosted by the RMO and the Goddard Space Flight Center in Greenbelt, Maryland,and will be held at the University of Maryland, College Park Campus Conference Centerin the Washington, D. C. area. This will be the first step in evaluating the utility of theprogram and its ultimate potential.The two-day workshop will provide an introduction to the ISS orbital and operationalenvironment, and address the capabilities of potential free-flyer platforms. Options forimplementing such a program within today’s tight budget environment will be discussed.To maximize the ability to deliver performance at low cost, various concepts to reuseexisting hardware have been explored and will be discussed. A summary of the scienceinstrument concepts that have been submitted prior to the meeting will be presented.Following these plenary sessions, the workshop will operate in parallel sessions allowingparticipants to discuss the presented information, assess the science mission concepts, andprovide recommendations. Reports from all the parallel sessions will be summarized at theconclusion of the workshop. Proceedings will be subsequently prepared and distributed.We would like to solicit your interest in such a workshop. We have set up an InternetWorld Wide Web (WWW) homepage atthat provides the most current information. You will find a survey and registration formthere that you may want to complete as soon as possible so we can benefit from yourthoughts.Depending on the recommendations from this workshop, the program may be incor-porated into existing opportunities. For example, should such a platform exist, proposersto the MIDEX program may have the option to propose an instrument to fly on theplatform.lllT H E  A D V A N T A G E S  T O  N A S ADemonstrates the benefits of bringing together NASA’s major elements: ISS, STSand science; to produce greater scientific discoveries at the lowest possible cost.Establishes the ability of ISS to become our assembly and servicing depot in space:the cornerstone in space exploration for the 21st century.Illustratespreviouslythe frugality and cost consciousness of the agency through the reuse offlown hardware with ISS.Lower life-cycle cost through reuse and periodic repair of assets.4-32F O R  F U R T H E R  I N F O R M A T I O N, C O N T A C T :E D W A R D  S. CH E N G,  NASA/GSFC CO D E  685 ,  301-286-5038R O N A L D  S. PO L I D A N,  NASA/GSFC CO D E  681 ,  301-286-5039F R A N K  J. CE P O L L I N A,  N A S A / G S F C  CO D E  4 4 2 ,  3 0 1 - 2 8 6 - 1 2 6 6J A M E S  R. BA T E S,  NASA/JSC CO D E  O K ,  7 1 3 - 2 4 4 - 7 0 3 14-33

Paper Session II-A - Free-Flying Platforms for the International Space Station: Large Aperture Science at Medium-Explorer Cost

https://commons.erau.edu/cgi/viewcontent.cgi?article=1551&amp;context=space-congress-proceedings

Paper Session II-A - Free-Flying Platforms for the International Space Station: Large Aperture Science at Medium-Explorer Cost

Abstract

Similar works

Full text

Available Versions

Embry-Riddle Aeronautical University