Anz-Meador, P.

Matney, M.

NASA Technical Reports Server

P. Anz-Meador1 and M. Matney2
1Jacobs, NASA Johnson Space Center, Mail Code XI5-9E, Houston, TX 77058
2NASA Johnson Space Center, Mail Code XI5-9E, Houston, TX  77058
Spacecraft Anomalies and Failures Workshop
11-12 December 2018, Chantilly, Virginia
Space Debris Sensor Recent Anomaly Attribution 
Scenario
-or-
A Cautionary Tale of How, While Trying to Measure the 
Source of One Type of Anomaly, We Ended Up 
Experiencing Anomalies of a Completely Different Kind…
https://ntrs.nasa.gov/search.jsp?R=20190000072 2019-08-30T04:50:43+00:00Z
National Aeronautics and Space Administration
2
SDS Introduction
• The Space Debris Sensor (SDS) is an instrument 
designed as a part of the DRAGONS program by NASA’s 
Orbital Debris Program Office (ODPO) to provide 
statistical in situ data on the orbital debris population 
that is too small for ground-based remote sensing 
– Information on debris ranging from 50 µm to 500 µm+ 
in size
– Estimates of this small debris population are currently 
based on inspection of exposed surfaces returned on 
Shuttle (retired 2011)
– Technology intended to provide data to be used to 
update the NASA Orbital Debris Engineering Model 
(ORDEM)
National Aeronautics and Space Administration
3
Orbital Debris Measurement Coverage:  SDS to address 
Data Gap at ISS altitudes as a technology demonstration
10 mm 100 mm 10 cm 1 m1 mm 1 cm
Particle Diameter
100
1000
10,000
36,000
10 m
2000
Goldstone radar
Haystack radar
Haystack Auxiliary (HAX) radar
U.S. Space Surveillance 
Network
HST-WFPC2 (580x600 km, 93-09)
STS (300x400 km, 95-11)
(Boundaries are notional)
MODEST 
telescope
Data Gap
National Aeronautics and Space Administration
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• SDS combines dual-layer thin films, an acoustic sensor system, a resistive 
grid sensor system, and sensored backstop to provide real-time impact 
detection and recording capability
– Impact event observable data includes: Impact times, impact locations, hole size, and 
backstop energy/impulse
– Derived data includes: particle size, impact speed, impact direction, and qualitative and 
quantitative particle mass density
How Does SDS Work?
Acoustic Sensors
Impact time & location
Dual-layer Films
Time of flight
Resistive Grids
Damage/Size
Incoming MMOD
Backstop
Impact Energy
National Aeronautics and Space Administration
5
SDS Introduction and Goals
• First flight demonstration of the Debris 
Resistive/Acoustic Grid Orbital NASA-Navy Sensor 
(DRAGONS) developed and matured by the ODPO
– While other debris sensors have been flown 
before, this combination of technologies to 
thoroughly characterize the debris is 
unprecedented
– The first flight demonstration in what is hoped to 
be a new generation of operational sensors flying 
at higher altitudes to fully characterize the debris 
environment
National Aeronautics and Space Administration
6
SDS Introduction and Goals
• The Space Debris Sensor (SDS) is a Class 1E NASA 
technology demonstration external payload aboard 
the International Space Station (ISS) 
– Limited budget
– Accelerated schedule
– Risk-managed experiment
• Primary goal – Technology demonstration
• Secondary goal – Take environment data
National Aeronautics and Space Administration
7
NASA Class 1E Hardware Overview
• “E” for Experimental
• New flight hardware classification intended to 
streamline flight certification
• All the risk is assumed by the funding authority, in 
this case, the ISS Program Office (ISSPO) 
• Payload shall not perform mission critical functions
• Shall not compromise safety of ISS crew or vehicle 
or SpaceX Dragon launch vehicle
• This hardware classification development and 
deployment coincident with SDS development life 
cycle
• Also motivated by NASA Revolutionize ISS for 
Science and Technology (RISE) initiative
National Aeronautics and Space Administration
8
SDS Overview
Principal Components & Vital Statistics
• Weight:
– Total: 267.69 kg / 590 lbs
– CEPA: 117.94 kg / 260 lbs
– SDS: 149.75 kg / 330 lbs
• Size:
– External Height: 67.56 inches 
– External Width: 47.92 inches 
(CEPA with handrails)
– External Depth:  53.00 inches 
(CEPA with handrails)
• Power
– 40W: SDS operating without 
heaters
– 155W: SDS operating with ISS 
heaters
– 100W: SDS non-operating with 
launch heaters
Columbus External Payload Adapter 
(CEPA; SpaceX OEM, SDS GFE)
SDS 
electronics 
box
SDS 
sensor 
assembly
National Aeronautics and Space Administration
9
SDS Installation on ISS
• SDS launched on SpaceX 13 (Dec. 2017) and was robotically 
installed on 1 Jan. 2018
• Installation on the Columbus External Payload Facility (Col-EPF) 
in the ISS forward-facing (ram) direction  
National Aeronautics and Space Administration
10
SDS ISS Orientation
Zenith
C
o
l-
E
P
F
Nadir
Starboard Port
National Aeronautics and Space Administration
11
SDS Concept of Operations
C&DH Verification
Testing on PRCU
Launch Vehicle
I&T at KSC 
Launch on
SpaceX 13
SpaceX Powered
Flight
SpaceX Rendezvous
With ISS SDS Unberth
Monitor Health &
Status Plus Control
Command And Data
Paths
Controllers at JSC
Monitor SDS Status and,
Send Commands via TReK;
Analyze Data
End of Mission
Uninstall and Disposal
Install SDS on Col-EPF SOX
MMOD
Impact
Impact produces
acoustic waves and
resistance changes
2-3 Years On-Orbit
Operational Life 
National Aeronautics and Space Administration
12
Timeline
• Initial checkout confirmed that all command and data 
interfaces were operational
• After hours of normal operation, SDS Health & Status 
data stopped updating and SDS did not respond to 
commands (Anomaly 1)
– Some of the software was still functional, because packets of 
information were still coming off of one interface
– However, command and control were no longer functioning
– Did not respond to software reboot commands
• The ODPO team determined that the only remaining option 
was to recycle the power
– A power recycle returned SDS to normal operations
National Aeronautics and Space Administration
13
Timeline
• We were able to replicate the lockup using the ground unit, 
and identified it as a software issue
– However, the instrument was not designed for software update
– The original cost estimate to have software configurable was 
determined not to be within the financial constraints of the program 
• The partial software lock repeated itself irregularly
– The power recycle was repeated each time the SDS Health & Status 
data stopped (65 times over 25 days)
• Finally, on January 26, 2018, SDS did not recover from three 
consecutive power recycle attempts (Anomaly 2)
• Attempts at power up between February 9, 2018 and June 26, 
2018 were also unsuccessful
National Aeronautics and Space Administration
14
Anomaly Resolution
• The initial loss of Health & Status was identified as a 
partial software locked-up state
• Investigation focused on finding an indicator to 
preempt the lock-up by issuing a software reboot 
command
• Software bug was identified in a commercial software 
module that had passed multiple software tests 
during development testing
• While final software configuration successfully went 
through communication and full functional testing, a 
test of long enough duration to manifest the problem 
was not repeated for final configuration
National Aeronautics and Space Administration
15
Anomaly Resolution
• There were several attempts to restore functionality, 
but there was no further response from the 
instrument
• As a direct result of the anomaly investigation (but 
after the fatal shutdown) a work-around was 
discovered whereby the software could have been 
updated in orbit prior to Anomaly 2
– This would have allowed us to correct Anomaly 1, 
preventing the need for frequent power cycling
– This method could be used in the future on ISS 
experiment packages using similar 
communications software
National Aeronautics and Space Administration
16
Summary
• Efforts through June 2018 were focused on recovery
– Lessons learned being compiled
– Beginning to look into science data – small impacts were seen 
• SDS experienced two types of anomalies
– Anomaly 1 locked-up the software to a point where commanding and 
science data collection were not possible until a power cycle reset 
the payload
– Anomaly 2 is of an unknown cause when SDS failed to reset or 
respond after an operational power cycle 
• Other discrepancies have been identified, but it is not clear yet 
whether they are related
– Only one of the two heater circuits seems to be working
– Heater current draw is less than predicted
– Some wiggles in data telemetry
• All 40 acoustic sensors and all 32 resistive grid circuits were 
functioning and collecting good science prior to second anomaly
National Aeronautics and Space Administration
17
Preliminary Lessons Learned
• Most probable cause of lost communication (Anomaly 2) was a 
hardware failure of the memory storage on the main interface 
processor
– Failure may have occurred due to repeated power cycles or 
environmental effects (radiation, plasma, etc.)
• The software bug in the file management software passed 
several tests during development.  Changes to the software 
caused the problem to manifest
– Additional long duration software testing pre-launch would have 
discovered the problem prior to flight
• SDS was not designed with a software update capability due to 
cost
– During anomaly resolution, the team learned that a low cost 
capability could have been added
National Aeronautics and Space Administration
18
Technology Demonstration Summary (to date)
• Collected over 1300 acoustic detection files and 26 days of 
resistance/engineering data 
• Demonstrated impact detection in the flight environment
demonstrate the detection 
component ground testing flight experience
Impact Detection P P
impact time P P
impact location P P
projectile direction P ?
projectile speed P ?
projectile size P ?
projectile density (via impact 
energy)* P ?
* Projectile density may be demonstrable in a qualitative sense by number of layers penetrated
• Because we only 
had 1 month of 
data, we have 
not yet identified 
any impacts 
large enough to 
confirm these 
capabilities in 
space
National Aeronautics and Space Administration
19
Conclusions
• SDS was a technology demonstrator flight payload 
– Demonstrated DRAGONS sensor technology for MMOD environmental 
measurements 
– Anomaly #1 did not compromise this demonstration 
• Analysis of SDS Health & Status and Science data continues to inform 
– Anomaly resolution effort (complete)
– General sensor-related engineering issues 
– MMOD environmental measurement
• Source of Anomaly #2 is still unknown
– Possible that power cycling contributed to it, but no way to confirm from 
available data
– Plausible environmental factors could have contributed to ultimate failure (e.g., 
radiation)
• Lessons Learned informs ongoing DRAGONS-type instrument  development
National Aeronautics and Space Administration
20
Example of Flight Impact Acoustic Data
National Aeronautics and Space Administration
21
Example of resistive grid temperatures
National Aeronautics and Space Administration
22
Example of potential line break


Space Debris Sensor Recent Anomaly Attribution Scenario

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