Micro-Gravity Tele-Presence Onboard Device
(µG telePOD)
For use Aboard the International Space Station
Gregg Podnar - Mel Siegel
July 1997

We describe a small, teleoperated robot for use in microgravity (µG) environments such as those found onboard the Space Shuttle, and the International Space Station (ISS).  The primary function of this device is to allow scientists and others on the surface to interact with science packages and crew on orbit.  Providing this capability allows experts to be present on orbit without the need to lift them there.  By employing self-mobile telepresence devices, a number of benefits are possible including
 - reduced need to rely on limited crew time to monitor science packages.
 - reduced crew training requirements in the setting up and operation of science packages.
 - more immediate monitoring of science packages by the ground-based investigators.
 - remote inspection of space station systems by ground-based engineers.
 - opportunities for students, family, and the media to experience the environment.
The integration of a number of current technologies is necessary for the successful deployment of µG telePODs. These include, for example, high-fidelity stereoscopic imaging both for inspection and for remote control; and binocular video stream compression to minimize bandwidth requirements.  Ground stations for remote control and monitoring are based on readily available hardware to allow many sites shared access to each µG telePOD.
Figure 1.

Our experience building robots that, collectively, have tested most of the components of a µG telePOD, indicates that the development of such a telepresence system is tractable and can be accomplished in a reasonable time and cost.  Manipulation capabilities of the device will be limited to minimize the development costs and improve overall reliability.   Once the device is proven to be reliable, additional capabilities can be added.

Features of the Device

The on-board environment of a facility such as the ISS lends itself well to the deployment of small, wireless mobile robots.  Refer to Figure 1 along with the following descriptions

Mobility can be elegantly achieved by taking advantage of both the microgravity and the atmosphere in the space station modules.  Simple fans, simply controlled, orient and propel the device.  We envision the µG telePOD as a five-degree of freedom platform with control for roll, pitch, yaw, translation fore and aft, and vertically.  It will be wireless, allowing travel to all parts of the environment.
Vision is provided by the stereoscopic camera system with a true, three-dimensional view, facilitating accurate movement and positioning as well as the realistic monitoring of the setup and operation of science packages.  Audio is stereophonic to enhance the reality of presence and assist in navigation.  Audio output provides a means for the operator to communicate verbally with crew members.  Other sensory modalities, e.g. "smell" (gas analysis) can be provided as needed or potentially needed.  See "Additional Optional Features".
Even without explicitly providing manipulators ("arms" and "grippers") the µG telePOD need not merely be an ineffective observer of the environment.  By taking advantage of the device's mass and accurate mobility, some amount of manipulation is possible, limited only by the imagination of the operators and crew.

Primary in manipulation is the multi-purpose snout.  It can be used to point at or touch items the operator wishes to identify to a crew member.  It can press on objects (ramming speed may be necessary to push a high-actuation-force button).  By the addition of a lanyard, the device can be used to pull on objects (such as yanking the handle of a small lever switch).  A loop attached to any free object, such as a tool, clipboard, or even a stowage bag, allows the µG telePOD to be used to transport items from one part of the station to another without the need for a crew member to carry it.  And so forth ...

The snout also provides a grapple for the support hardware to position the device for service changing batteries, cleaning lenses, &c.

 Additional and Optional Features
Bright headlights allow the operator good visibility even in poorly lit areas.  A visible laser pointer further allows the ground-based scientist to point at objects when discussing with crew members.  A sonar range sensor allows further confirmation of relative position which may be useful when attempting accurate positioning.

A stereoscopic micro/endoscope may be added inside the snout for extreme closeup inspection.  The normal stereoscopic camera system provides a proprioceptive view to align the snout (it can see it's own nose), and then the operator can switch to the microscopic view.  A fibre-optic illumination system can serve double duty both for the endoscope and as a near spot illuminator.

Temperature, humidity, smoke, and toxic gas sensors may also be incorporated into the µG telePOD.  Micro-manipulators may be added for delicate tasks.  Tanks for small quantities of gases or fluids may be added and dispensed when required.  Clearly, a variety of optional sensors and effectors can be considered given the µG telePOD as an effective remote-controlled mobile base.

Basic Design

The initial device is designed within a volume defined by a 7 inch (18 cm) diameter sphere.  Smaller and larger devices are possible, of course, but this reasonably small size allows use of many off-the-shelf parts, and proper spacing of cameras and microphones for realistic telepresence.

The fans associated with pitch and yaw are all oriented to the fore-aft axis of the device (see Figure 2), thus allowing the majority of the fans to contribute to propulsion.  This supports more rapid movement when traveling long distances.  Fan-pairs when run together produce translations, while fan-pairs run in opposition produce rotations.  Variable speed fans are employed to allow fine control forces.

The main body of the device is comprised of resilient, space-qualified foam.  This

Figure 2 (cutaway views).

provides cushion for the inevitable bumps into walls, as well as protection against rough handling by the crew.

Control electronics include drivers for the fans, switches for lights, selection and interfacing of sensors, &c.  The wireless link is initially planned to use radio, with other wireless technologies (e.g. IR) under consideration.  Battery life, speed, and other performance characteristics are dependent on usage and can be decided given specific mission requirements.

Design considerations for extraction and replacement of batteries allow a variety of battery placements.  By centrally locating the batteries (the greatest mass), rotations about the device's origin can have higher acceleration and be easier to stop over-shoot.  Should other control philosophies later seem more natural, this mass can be distributed to the periphery to adjust these handling characteristics.


An on-board support locker for the µG telePODs will minimize crew time demand.  The ground-based teleoperation stations are designed to minimize training requirements for the scientists, virtual crew, and visitors.

 Onboard Support of the µG telePOD
For feasibility testing and short missions, the only additional support system is the interface into the shuttle or ISS ground communications.

For long-term missions, to further minimize impact on crew training and time, the µG telePODs are serviced remotely from the ground.  A service bay, mounted in a standard locker, also provides storage for the devices during lift.  In normal operation, the operator flies the device to the service bay, which grapples it by the snout, orients it, changes the batteries, cleans the lenses if necessary, and allows general inspection.  The wireless links originate at the service bay and interconnect here with the ISS's support facilities.

 Ground Stations for Scientist / Operators
The ground stations for teleoperation of the µG telePODs are based on a desktop computer workstation.  Decompression of the stereoscopic video stream and audio streams is accomplished in software.  Presentation of the stereoscopic video is provided both on a monitor using flickerless stereoscopic shuttering eyewear, as well as a head-mounted stereoscopic viewing system.  Roll, pitch, and yaw movements are joystick controlled, or can be coupled to a three-axis mouse mounted to the headset.  Propulsion can be tied to a joystick or foot pedals, again, all readily available.  A variety of other controls are available in software for optional devices and the monitoring of additional sensors.

By basing the ground stations on readily available hardware, cost is minimized and multiple stations may be made available to scientists and other operators who then share time visiting the ISS as virtual crew members.

It is also possible to monitor and control the device at a much lower fidelity via a Web page.  This would allow a very great number of potential visitors (especially well suited to students).

Figure 3.

Issues to be Resolved

The stereoscopic video, stereophonic audio, and sensor and telemetry data are carried on frequencies dependent on the ISS system specifications.  Bandwidth within the ISS, and down- and up-link bandwidth are to be determined through interaction with ISS system designers.  Down-link bandwidth (the majority of data flow) needs to be real-time with minimal frame delay.  New compression techniques for stereoscopic video streams combined with graceful resolution/bandwidth tradeoffs when necessary, will provide the best experience possible to the scientists.

A research component to the development of the µG telePODs is determining the capabilities and preferred interfaces for devices actually flying in microgravity environments.  Missions on the Space Shuttle will provide the environment for such experimentation.


A number of limitations are inherent in a facility such as the ISS.  Cost to support life in the hazardous environment of space, and cost to lift weight into orbit are two.  With so rich an opportunity for research, and so high a price for putting scientists there, telepresence is an ideal technology to exploit.  It's application allows a limitless number of experts to 'fly'.  And by providing this access to virtually anyone, many forms of additional interaction become available with minimal additional impact on mission requirements.

The ability of a scientist to be present with a crew member in the setup, operation, restocking, and repair of experiment packages is fundamental to the successful outcome of the research.  Crew time in training and carrying out procedures for each of the many experiment packages is lessened by having the expert present to assist.  Additionally, the µG telePODs allow additional ground-based crew to be present on-board for inspection, systems monitoring, and consultation.  This also allows experienced engineers to directly assess conditions and more effectively determine actions for maintenance as the ISS ages.

Safety is another area where the µG telePOD may serve the needs of the crew.  Should there be an ISS module which becomes dangerous to the crew (such as by contamination), the device may be able to provide remote assessment, monitoring, and possible other uses.

The "visits" of family, educators, students, and the press, allow interactions with members of the crew unlike any before possible.  In addition to the reality of on-orbit presence for the visitors, their more-tangible presence as embodied by the mobile vehicle and verbal communication may also serve to lessen some of the psychological pressures experienced by long-term assignment of the space station crew.  To ensure safe 'driving' by naive operators, a layer of monitoring and control software can be provided.


We describe a system for telepresence on the International Space Station and the Space Shuttle with many benefits and with relatively low costs (to budgets of money, weight, space, and mission).  Adoption of µG telePOD technology by NASA opens up new avenues of research, ensures that planned research is effectively executed, and provides access to many individuals who would never otherwise have personal experience of space.


This description of the µG telePOD is an outgrowth of the NASA Microgravity Technology Workshop, held 14-16 January, 1997, at the National Technology Transfer Center, Wheeling WV.

Gregg Podnar
Sr. Research Engineer

Mel Siegel
Senior Research Scientist

The Robotics Institute
Carnegie-Mellon University
Pittsburgh, PA 15213
(412)268-5569 Fax