Findings & Concerns

Meeting of December 19, 2001
Sounding Rocket Working Group
National Aeronautics and Space Administration

1.  New Technology Recommendations  --  An Initial List

General Considerations

The Sounding Rocket Working Group has been asked to consider which new technologies it believes Wallops should pursue in order to maximize the science return of future missions.  In particular, we seek to identify which new technology thrusts might open the door to completely new areas of research which would thus become immediately appealing to the scientific community, and by extension, to the Office of Space Science at NASA Headquarters.

The SRWG provides an interim list of new technology recommendations below.  No attempt was made to canvas the community for their input that we view as essential to this process.  Prior to taking this step, however, the SRWG feels that it is important to understand the budget available for the new technology development as well as the time-table.  We would also like to better understand how NSROC decides on which new technologies to pursue and how it diverts/invests funds in these areas.  For example, are direct NASA funds, marketing funds, overhead funds, and/or R and D funds used for these new initiatives?  Are new technologies selected for development based on user needs or future marketing potential? 

Although mindful of the rocket program’s fiscally constrained environment, the SRWG wholeheartedly believes that new technology thrusts are essential for keeping the program viable and at the cutting edge of important scientific research.  We thus enthusiastically participate in this activity and look forward to working with the Sounding Rocket Program Office, NSROC, NASA HQ, and the science community in promoting those new technology initiatives that show the most promise for advanced scientific research in the future.

We have divided our technology recommendations into two categories:  (1) Critical technology that is needed to maintain or improve existing payload systems, and (2) New Technology Thrusts.  As outlined below, we believe that there is a real crisis concerning the current capabilities involving ACS and attitude systems as older hardware used for decades in the program, as well as their standard contractor suppliers, may no longer be available.  In some cases, this critical technology must be provided immediately as several approved programs are relying on such sub-systems for success.

I.  Critical Technology to Maintain and/or Improve


*  A.  Fine pointing ACS systems for Astronomy and Solar Payloads

*  B.  Coarse Gyro and ACS for Space Physics Payloads


II.  New Technology Thrusts


A.  Astronomy/Planetary/Solar Physics


*  1.  More time on target

2.  Improved fine pointing, stability, and target acquisition time

3.  Payloads to accommodate larger diameter telescopes

4.  Long baseline interferometry using multiple telescopes


B.  Space Physics


*  1.  Small Payload and Launcher (e.g., Viper Dart) Development

*  2.  Multiple Payload Technology

*  3.  Higher Data Rates

4.  Guided Trajectories

*  --  Discussed below.


 I.  Critical Technology to Maintain and/or Improve

Fine pointing ACS systems for Astronomy and Solar Payloads

The most common fine pointing ACS configuration used on sounding rocket astronomy payloads is the Aerojet Mark VI platform with a Ball star tracker, which yields a typical pointing stability of 5 arc sec rms.  We note that recent advances in ground- and space-based spatial resolving power are routinely below 1 arc sec.  The SRWG believes that the next generation sounding rocket fine point capability should be better than 1 arc sec to remain competitive with the rest of the field.  Towards this end, a new digital Mark VI was flown in October 1999 on Cruddace 36.162 DG and provided excellent performance.  It is equally important to improve the pointing accuracy of the ACS star tracker.  The current Ball star tracker has a number of limitations, namely a 4th magnitude brightness limit, the ability to track only 1 target within a 4 degree field of view, and a noise equivalent angle of 3 arc sec at Oth magnitude that grows to 9 arc sec at 3rd magnitude.  In addition, these trackers are dwindling in number due to recent failures and are no longer manufactured.

A new star tracker and ACS system that can quickly identify where the telescope is pointed without the need for guide star acquisitions can increase the net observing time by up to 20% or 60 seconds. This new star tracker must track multiple faint targets within the same field of view and be functionally compatible with the digital Mark VI.  Commercial star trackers tend to be expensive; in the $100K -- $1M range.  Given the limited resources of the sub-orbital program, we believe an alternative source for star trackers is required that can address the immediate need for replacement star trackers and provide enhanced capability in the near future.

Such an effort is being lead by Drs. Kenneth Nordsieck and Jeff Percival at UW-Madison who are developing a cost effective alternative to the existing star tracker, as noted in the detailed SRWG finding on this subject from its June, 1999 meeting.  The effort has been largely funded by NASA through an Explorer Technology Grant.  The UW team has made considerable progress in developing and testing a direct replacement to the Ball star tracker with the aforementioned capabilities.  Their system, known as the ST5000, has flown twice, in each case side by side with the Ball tracker and provided impressive results.

The SRWG strongly feels that the ST5000 is a viable and mature option for the sounding rocket community and recommends that NSROC aggressively pursue using the ST5000 to replace the Ball star trackers.  The ST5000 addresses many of the recommendations by the SRWG:  it can be used as a direct replacement for the Ball tracker and can identify where it is pointed within 2-6 seconds without the need for multiple guide star acquisitions.  This second capability is important for increased observation time.

Coarse Gyro and ACS for Space Physics Payloads

Next Generation ACS Systems/Coarse-Pointing

The SRWG finds much need for improvement in the utilization of coarse-pointing ACS systems on sounding rockets.  As noted in our previous finding on this subject from the June, 1999 SRWG meeting, there is a range of operation problems regarding the use of coarse-pointing ACS systems including inertial pointing inaccuracy and firing at inopportune times, including times inside the dead band.  These types of ACS problems can lead to serious compromise of the science objectives because instruments are not oriented as desired and/or the firing operations disturb the scientific measurements.  There is now the added concern that the regular supplier of these ACS systems, Space Vector Corporation, may not be able to provide these systems on a cost effective basis in the future.

The SRWG urges NSROC to develop a plan to provide new “coarse” ACS systems for space physics payloads.  Such systems must be dependable, lightweight, easy to implement, capable of achieving a payload orientation in a short amount of time, not continuously disruptive of scientific instruments, and inexpensive.  In general, space physics ACS systems must perform one of two tasks:  (1) line the payload spin axis with the ambient magnetic field vector, or (2) follow a pre-programmed set of orientations such as lining the ram axis with the velocity vector on the upleg and downleg.

In the case where the ACS need only line the payload spin axis with the ambient magnetic field, a very simple system with a straightforward comparator circuit is needed to achieve the required alignment which is usually +/- 1 degree.  In fact, NASA/Wallops Flight Facility used to build such analog magnetic ACS systems with a very high degree of reliability and low cost.  The SRWG urges NSROC to consider flying the old “tried and true” systems for which the detailed drawings are still available at Wallops.  Since space physics payloads are not routinely recovered, it is also paramount that NSROC develop an inexpensive ACS system (such as the analog magnetic system mentioned above) that it can afford to throw away.

Next Generation “Coarse” Attitude Systems

Another area of long-standing concern of the scientific user community and the SRWG in particular involves “coarse” (i.e., ~ 1 degree knowledge) attitude solutions, as also noted in the Findings from the June 1999 SRWG meeting.  These attitude solutions are frequently supplied to the science teams only to be subsequently determined to be inaccurate.  Consequently, a great deal of effort is expended by the science teams to both verify and develop acceptable solutions which should, in principle, be an accurate data product when delivered to the science team.  Our greatest nightmare involves the publication of an incorrect scientific result that results from an erroneous attitude solution that was either never verified or improperly verified.

The standard payload system used to provide coarse attitude knowledge for most space physics payloads is the MIDAS gyro platform and its derivitives.  These systems utilize designs that are over 25 years old and which are also made by Space Vector Corporation.  We urge NSROC to develop a plan whereby accurate, inexpensive, and lightweight alternatives are available for those times when the MIDAS platform is no longer available or affordable.  As with any new ACS system, it is essential that rigorous testing be carried out of the new attitude system, including the verified analysis of the attitude data, prior to its instigation in the program.

II.  New Technology Thrusts

A.  Astronomy/Planetary/Solar Physics

More time on target

For astronomical payloads, the flight time above the altitude where emissions are absorbed by the Earth's atmosphere (typically ~100 km) directly determines the signal obtained from the target.  Most of these payloads are UV stellar and solar telescopes launched from WSMR, and there is a clear advantage to a longer "hang time".  We note that even 60 second of extra hang time can significantly improve the science return on astronomical and solar missions by providing additional target opportunities.  A doubling of the hang time would be equivalent to flying a telescope with a diameter 1.4 times larger than what exists, and lead to a similar improvement in the signal/noise.  The tight impact dispersions achieved with the recently developed DS-19 opens the possibility of flying vehicles with higher trajectories, such as the BB-X, -XI, or XII, at WSMR.  New parachute systems are also needed to accommodate the larger re-entry velocity environments, and in this regard we note the impressive recovery operations of the high altitude (750 km) MAXUS payloads launched on the Castor IVB motor within the narrowly constrained Esrange launch area in Sweden.  The SRWG strongly urges NSROC to fully analyze the technical and logistical issues surrounding the launch and recovery of astronomical payloads at WSMR using higher performance vehicles and to develop an implementation plan for this enhanced capability.

B.  Space Physics

Miniaturized Payloads and Small Launchers

Small, miniature platforms enable important new in-situ scientific measurements to be carried out in the mesosphere and lower ionosphere repeatedly and at low cost.  Because of their small size, such payloads would perturb the medium to a minimum extent and would thus enable new types of measurements to be carried out.  Because of their low cost and portability, scientists would be able to launch numerous such rockets in a single geophysical event or a series of such rockets over a relatively short period of time.  The success of such a system relies on two engineering factors:  (1) the development of a reliable, low cost launcher, such as the Viper Dart and other small motors; and (2) the development of a small payload with reliable, low cost sub-systems, such as GPS receivers, power, magnetometers, attitude knowledge, etc.

Based on previous reports to the SRWG, it appears as if the Viper Dart instrumented payload promises to be a valuable mesospheric research tool, as demonstrated by the success of the Norwegian engineering and scientific teams with similar payloads.  We look forward to the successful NASA development of both a small launcher and miniature payload such that such systems might be routinely available to the scientific community via the AO process.

Multiple Payload Technology

Multiple payloads launched on a single rocket enable several exciting new areas of space physics research to be carried out.  Although “daughter” or sub-payloads have been used in the program for decades, only recently have sub-meter spatial knowledge and sub-microsecond temporal knowledge between platforms separated in space become possible.  Such inter-payload precision opens new avenues for investigating a variety of space physics phenomena, including wave data (for example, using in inter-payload interferometry), particle and fields electrodynamics (for example, solving curl equations with input from spatially separated payloads), and detailed differentiation between space/time causal effects (for example, with wave-particle interactions).

Such multiple payload technological advances have been pioneered by a number of individual research groups, including UNH, Cornell, and UCB, in recent years.  At this juncture, we urge NSROC to develop those sub-systems that might provide the necessary high precision spatial and temporal accuracies between multiple payloads so that they may be available routinely and inexpensively to the scientific community at large.  In particular, we urge that a small, lightweight, and inexpensive ACS system be developed for such sub-payloads.

Finally, we note that the new thrust of orbital missions in the Solar-Terrestrial Probes line as well as in the NASA Sun-Earth Connections Roadmap involve in-situ measurements gathered with clusters, swarms, and indeed constellations of payloads flying.  The slower speeds of the rockets and their direct engagement of known geophysical events observed simultaneously with ground-based instrumentation provide unique opportunities for sounding rocket experiments to be the forerunners of the larger class investigations and indeed, to enable high level data analysis techniques to be developed.  The SRWG thus acknowledges the pioneering role that the multiple sounding rocket payload technologies are playing for the development of a large new class of space experiments for the Space Physics community.

Higher Data Rates

With a few exceptions, scientific sounding rockets use telemetry for data acquisition. Some ongoing experiments have pushed the limits of telemetry rates supportable by Wallops engineering, and experiments which have exploited this capability to the maximum have produced exciting results. For example, key plasma resonance frequencies lie in the range 1-10 MHz in the ionosphere, and the ability to measure multiple components of fluctuating fields at comparable data rates has revealed for the first time the fine structure associated with these resonances.  However, the need for high telemetry rates is not limited to wave experiments. Recently, imaging auroral and other phenomena has emerged as a top priority, with several groups proposing.  Imagers, particularly when operated at high speed as must be done in state of the art science experiment, produce prodigious amounts of data and will push the bandwidth requirement.  Another important frontier in space sciences and astrophysics can broadly be defined as "high energy resolution at high energies," whether measuring particles or photons. This challenge inevitably requires extremely high bandwidths.

With these trends clearly in view, the NASA sounding rocket support at Wallops should consider a significant qualitative upgrade in the data acquisition to rates 10-100 times greater than those available today.  Although it might require an investment in new ground equipment, this upgrade would pay off in a large jump in the quality and quantity and excitement of science experiments performed within the rocket program.  Acquiring broader bandwidth telemetry is one way to achieve this enhancement.

2.  Wallops Geophysical Observatory

The SRWG was very pleased to hear the progress report on the Wallops Geophysical Observatory which consolidates a number of existing and planned ground based instruments at Wallops and provides a web-based distribution center for all of the data.  The existing instruments include the SPANDAR radar, ionosonde, field mills, lightning detector, and meteorology.  New instruments include a sensitive magnetometer, GPS receivers, and possibly a series of SPANDAR enhancements.  Such scientific instrumentation not only provides valuable knowledge concerning the atmosphere and ionosphere in support of flight programs at Wallops, but also provides a long term baseline in which the flight data may be placed in context.  Further, the instruments provide continuous measurements at a key mid-latitude site that will be accessible to the entire science community.  We applaud the work of the Wallops Flight Facility staff in their creation, maintenance, and fostering of the Wallops Geophysical Observatory.

3.  Emulator for the WFF93 Telemetry System

Wallops has been working with PSL for several years to create an emulator for the WFF93 telemetry system that would allow experimenters to develop and test their interfaces before arriving at Wallops for integration.  The most important interface is the serial telemetry interface, as that is the one that is most difficult to work with.  The SRWG would like to commend Wallops for this work, as several benefits are likely to come from such a development, including more efficient use of time and money at the experimenter institutes and at Wallops, and the flight of more reliable systems.  However, although this development has been discussed at several SRWG meetings, the emulator has yet to be finished and distributed.  The SRWG thus encourages NSROC to take a more active role in assuring that this new system will be delivered in a timely fashion so that experimenters can begin to take advantage of its important and tremendously useful capabilities.

4.  Appreciation  --  Mr. Bobby J. Flowers

The Sounding Rocket Working Group expresses its sincere appreciation and deep gratitude to Mr. Bobby J. Flowers, who managed the program so well over the past five years and who retired earlier this year.  Bobby worked for over 40 years in the rocket program, including many years as a payload manager.  The Sounding Rocket Working Group acknowledges in particular the contribution of Mr. Flowers who served as the Sounding Rocket Program Chief during a difficult time which included the initiation of the NASA Sounding Rocket Operations Contract at Wallops and a significant perturbation in program funding.  The sounding rocket program that Bobby Flowers helped create has enabled unique scientific achievements to be carried out in space, reflecting highly on both NASA and the United States.  We acknowledge Bobby’s expertise regarding sounding rocket systems and thank him for his untiring dedication to the program.


NASA Sounding Rocket Working Group

Dr. Robert F. Pfaff, Jr. (Chair)
NASA/Goddard Space Flight Center

Dr. James Clemmons
Aerospace Corporation

Dr. Joseph Davila
NASA/Goddard Space Flight Center

Dr. Greg Delory
University of California at Berkeley

Dr. James LaBelle
Dartmouth College

Dr. Kristina Lynch
University of New Hampshire

Dr. Stephan McCandliss
Johns Hopkins University

Dr. Scott Porter
NASA/Goddard Space Flight Center

Dr. David Slater
Southwest Research Institute

Dr. James Ulwick
State University

Dr. Erik Wilkinson
University of Colorado