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Small Satellite Conference – Utah State University
STPSat-3: The Benefits of a Multiple-
Build, Standard Payload Interface
Spacecraft Bus
August 5, 2014
Kenneth Reese DOD Space Test Program
SMC, Space Development and Test Directorate
Alex Martin The Aerospace Corporation
David Acton Ball Aerospace & Technologies Corp.
Distribution A: Approved for public release; distribution is unlimited.
Page_2
STP-SIV program and current status
The Space Test Program – Standard Interface Vehicle (STP-SIV)
program is sponsored by the DoD Space Test Program
STP is the primary provider of spaceflight for the DoD space science and
technology community
Provides spaceflight and on-orbit operations for DoD experiments as
prioritized by the Space Experiments Review Board (SERB)
SMC/SD awarded an Indefinite Delivery Indefinite Quantity (IDIQ)
contract to Ball Aerospace for rapid acquisition of satellites
Ball Aerospace is the prime contractor with end-to-end responsibility
STP-SIV #1 (STPSat-2) currently in extended on-orbit operations
Launched 19 Nov 2010 on a Minotaur IV from Kodiak, AK
Supporting three DoD payloads
STP-SIV #2 (STPSat-3) currently in normal operations
Launched 19 Nov 2013 on a Minotaur I from Wallops Island, VA
Payload manifest completely re-defined to six unique payloads (DoD and NASA) less than one year before Pre-Ship Review
Design is now available commercially from Ball as the BCP-100
spacecraft bus
A contracting model that enables rapid technology advancement
STPSat-2
STPSat-3
Page_3
The Standard Interface Vehicle –
Designed, analyzed, and tested for mission flexibility
Spacecraft Parameter STP-SIV Capability
Orbit altitude 400 – 850 km
Orbit inclination 0° – 98.8°
Launch mass ESPA: ≤ 180 kg
SV dimensions (cm) 60.9 x 71.1 x 96.5
SV lifetime No life-limiting consumables
Reliability Ps = 0.93 @ 1 year; 0.81 @ 3
years; 0.71 @ 5 years
Stabilization method 3-axis
Pointing modes Nadir, Solar, Inertial, Ground
Track, Safe
Attitude knowledge 0.02° 3σ
Attitude control 0.03° 3σ
Bus voltage 28 V ± 6 V
Comm frequency S-band: Secure SGLS via AFSCN
Command rate 2 Kbps uplink (via AFSCN)
Telemetry rate 2 Mbps downlink (via AFSCN)
Robust configuration designed for variety of LEO orbits
ESPA compatibility increases launch options
Lifetime only limited by component reliability
Flexible pointing options allow for expanded mission
ConOps
Ball-heritage precision pointing algorithms
High-margin lithium-ion battery
Robust ground interface
Page_4
STP-SIV defined standard interfaces
Mission Ops
Center (RSC)
AFSCN
Launch Vehicle
• Multi-Mission SOC Ground Support Architecture
(MMSOC-GSA)
• Operating multiple missions on same ground system
allows reuse of command and telemetry databases
• Operators familiar with spacecraft operations
Spacecraft bus
Payloads
SIV Space Vehicle • Designed to SIS-00502
• Defines SIV RF system
• Pre-approved frequencies for future DoD SIVs –
allows production of “on-the-shelf” bus for
responsive space application
• Payload interface
standardization maximizes
SMC/SD’s ability to
manifest SERB payloads
• Documented standard allows
payload manifest process to run in parallel with spacecraft integration
• Reduced risk and schedule at payload integration
• Designed for wide range of primary and secondary launch
options (Minotaur I, Minotaur IV, Pegasus, ESPA)
• Maximizes SMC/SD’s spaceflight opportunities
• Powered off once integrated on LV, reducing LV interfaces
Page_5
Standard interfaces for rapid payload accommodation
Open-source Payload Users’ Guide
allows payload development without
intensive interaction
with bus provider
(similar to a Launch
Vehicle users’ guide)
Accommodation
Parameter
SIV Payload Support
Capability (total for all payloads)
Number of payloads Four. More with minor harness modifications.
Payload mass ESPA: Up to 70 kg
Dedicated launch: 100 to 120 kg (depends on
LV)
Payload orbit-average
power
200 watts (best case orbit)
100 watts (worst case orbit)
Payload volume ESPA: 0.14 m3
Dedicated launch: >0.93 m3 (depends on LV)
Payload field of view Clear 3 steradian (2 str each in the nadir
and anti-velocity directions)
Payload data handling Up to 2 Mbps per payload
Payload data storage 15.6 Gbit
Payload digital
command and data
interface
RS-422 provides high rate payload data,
command, and bi-level discrete input/output
Payload analog data
interface
8 analog channels per payload for health and
status
Payload heat rejection 100 watts
Six payloads demonstrated on STPSat-3
Robust mounting, electrical, and data
interfaces accommodate a wide variety of
payloads
S/C simulator with payload
interface electronics and
software available to
payload providers for risk
reduction testing
Page_6
STPSat-3 – the ability to flexibly adapt to payload changes
Jan 2009 – Bus started prior to payload manifest
June 2010 – Four payloads manifested post-CDR
SASSA (primary), SWATS, iMESA, SSU
Nov 2010 – SASSA inrush issues led to power
interface change
May 2011 – Interface issues between SASSA and
SSU led to significant delay
Sept 2011 – SSU direct interface box (IDL) begun
as risk reduction
Dec 2011 – SASSA withdraws from the mission
(80% of payload volume and 60% of payload
mass)
SSU IDL interface becomes baseline
May 2012 – J-CORE and TCTE manifested as
SASSA replacements
May 2012 – DoM manifested for de-orbit capability
Payload
Interfaces
Power
Data – RS-422
Data – Spacewire
Page_7
STPSat-3 – the ability to flexibly adapt to payload changes
Jan 2009 – Bus started prior to payload manifest
June 2010 – Four payloads manifested post-CDR
SASSA (primary), SWATS, iMESA, SSU
Nov 2010 – SASSA inrush issues led to power
interface change
May 2011 – Interface issues between SASSA and
SSU led to significant delay
Sept 2011 – SSU direct interface box (IDL) begun
as risk reduction
Dec 2011 – SASSA withdraws from the mission
(80% of payload volume and 60% of payload
mass)
SSU IDL interface becomes baseline
May 2012 – J-CORE and TCTE manifested as
SASSA replacements
May 2012 – DoM manifested for de-orbit capability
Page_8
Efficient requirements verification with the standard bus
STP-SIV design based on Technical
Requirements Document (TRD) containing
167 requirements on the spacecraft bus
STPSat-2 verifications leveraged to
streamline the STPSat-3 effort
Full system heritage of the bus made this
possible
STPSat-3 verification effort could focus on
the Mission Unique Requirements Document
(MURD)
Final payload manifest resulted in seven
unique payload ICDs
Development of individual payload ICDs was
efficient, leveraging the similarity of the
interfaces and lessons learned from prior
efforts
Confidence in the bus heritage allowed focus
on verifying compatibility on the payload side
of the interface
Spacecraft Bus Requirements Payload Requirements
TRD 167 TRD ~
MURD 68 MURD ~
SSU PL ICD 27 SSU PL ICD 56
IDL PL ICD 47 IDL PL ICD 71
SWATS PL ICD 52 SWATS PL ICD 73
iMESA-R PL ICD 52 iMESA-R PL ICD 73
TCTE PL ICD 51 TCTE PL ICD 74
J-CORE PL ICD 56 J-CORE PL ICD 72
DoM/SoM PL ICD 25 DoM/SoM PL ICD 56
TOTAL: 545 TOTAL: 475
Page_9
Heritage from STPSat-2 allowed very early start to the
requirements verification process
Many verification artifacts for the heritage bus were available and approved early on
Staggered submittal of sell-off packages (SOP) stretched the verification effort over a
longer period of time, avoiding a rushed effort just prior to Pre-Ship Review
Page_10
Lower inherent risk through use of the standard bus
Risk management focused on
STPSat-3 unique risks, most of
which were mitigated and closed
(white rows) Most risks carried forward from STPSat-2
(blue rows) were easily accepted without
further mitigation effort
Page_11
… 2010 2011 2012 2013 2014 …
25
20
16
15
12
10
9
8
6
5
4
3
2
1
# of identified risks with indiciated score
Ris
k Sc
ore
At launch, the program enjoyed a medium
risk posture, not typical for STP missions
Focus on mission specific risks led to low overall risk
posture for a technology demonstration mission
With STPSat-2 operating successfully on-orbit, the second
build had an inherent lower risk posture at inception
Page_12
Flexibility for short term launch opportunities
STPSat-3 bus integration underway
well before launch opportunity
identified
Key design features allowed launch
flexibility and quick manifesting on the
ORS-3 Minotaur I mission:
Overdesigned to allow wide range of
orbits
Standard LV interface (Motorized
Lightband)
Designed and tested to worst-case
environments of multiple LVs
With refined procedures, lessons
learned, and expertise from STPSat-2,
launch processing went smoothly and
kept STPSat-3 off the critical path to
launch
STPSat-3 atop the
ORS-3 Integrated
Payload Stack
Page_13
Commissioning efficiency leveraged standard
procedures and veteran operations team
Bus commissioning completed very quickly (72 hours)
All initialization objectives met according to the nominal schedule
Success directly attributable to lessons learned and implemented from
previous mission (STPSat-2)
Fast bus commissioning allowed prompt payload initialization
J-CORE was even turned-on
during first orbit
TCTE initialized on Day 5,
allowing full instrument check-out
prior to critical cross-calibration
with the Total Irradiance Monitor on
NASA’s SORCE mission in mid-
December
Page_14
Investment in standardization paid off on STPSat-3
STPSat-3 bus cost 37% less than STPSat-2 bus
Ball projects next BCP-100 bus would save
additional 35% from STPSat-3 bus cost
Key factors in cost reduction are staff continuity
and investment in documentation and GSE reuse
Reuse also results in significant schedule
reduction and responsiveness to external
stakeholders such as launch provider
Heritage reviews replace design reviews
Cost benefits extend to ground segment as well
Reuse of documentation (On-Orbit Handbook,
Space Vehicle Handbook, Space/Ground ICD)
Command/telemetry database virtually
unchanged
Carryover of telemetry screens and commanding
interface
Streamlined launch readiness/rehearsals
Page_15
The future of the Standard Interface Vehicle
Next BCP-100 flight: NASA’s Green
Propellant Infusion Mission (GPIM)
Will demonstrate Air Force-
developed high performance
“green” propellant alternative to
traditional hydrazine
Will also fly three SERB secondary
payloads
Launch expected Q2 2016
Applying lessons of STP-SIV to
even smaller standard vehicle
concepts
E.g. Ball’s BCP-50 sized for two
SERB-like payloads
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