unisat

Mission Design

Reference: ECSS-M-ST-10C (Project Planning), ECSS-E-ST-10C (System Engineering), CubeSat Design Specification Rev. 14

1. Mission Objectives

1.1 Primary Objectives

ID Objective Success Metric Priority
MO-1 Demonstrate modular CubeSat platform (1U-6U) Platform operates nominally for > 6 months Essential
MO-2 Earth observation with multispectral imaging >= 10 images at 30m GSD downlinked Essential
MO-3 Radiation environment monitoring (LEO) Continuous dose rate data for > 3 months Essential
MO-4 IoT message relay demonstration >= 100 messages relayed Desired
MO-5 Technology validation for ADCS subsystem 3-axis stabilization to < 1 deg accuracy Essential
MO-6 Technology validation for EPS subsystem MPPT efficiency > 90%, autonomous power management Essential

1.2 Mission Success Criteria

Level Definition Criteria
Minimum Success Basic platform operation Beacon received, TM downlinked, ADCS detumbled (MO-1 partial)
Partial Success Primary payload operates At least 1 image + 1 month radiation data (MO-2, MO-3 partial)
Full Success All primary objectives met MO-1 through MO-6 fully achieved over 12 months
Extended Success Beyond design life Operations continue past 24 months

2. Requirements Traceability Matrix (RTM)

2.1 Mission-to-System Requirements

Mission Req. System Requirement Subsystem Verification Status
MO-1 SYS-01: Operate for >= 2 years in LEO All A/T Open
MO-1 SYS-02: Mass < 4.0 kg (3U) Structure I Open
MO-1 SYS-03: Fit in standard 3U deployer Structure I Open
MO-2 SYS-04: GSD <= 30 m at nadir Camera A/T Open
MO-2 SYS-05: >= 10 images downlinked in 6 months COMM, Camera T Open
MO-2 SYS-06: Pointing accuracy < 1 deg (3-axis) ADCS T Open
MO-3 SYS-07: Radiation dose measurement 0.01-100 mGy/day Payload T Open
MO-3 SYS-08: Radiation data stored onboard >= 30 days OBC A/T Open
MO-4 SYS-09: Relay LoRa messages within footprint Payload T Open
MO-5 SYS-10: Detumble from 10 deg/s to < 0.5 deg/s in 3 orbits ADCS A/T Open
MO-5 SYS-11: 3-axis pointing with RW, < 1 deg accuracy ADCS A/T Open
MO-6 SYS-12: Positive energy balance in nominal mode EPS A Open
MO-6 SYS-13: Autonomous safe mode on low power EPS, OBC T Open

2.2 System-to-Subsystem Requirements

System Req. Subsystem Req. Allocated To Spec Value
SYS-04 CAM-01: Focal length >= 50 mm Camera f = 50 mm
SYS-04 CAM-02: Sensor >= 5 MP Camera OV5647, 2592x1944
SYS-04 ADCS-01: Pointing knowledge < 0.5 deg ADCS Sun sensor + magnetometer
SYS-05 COMM-01: S-band downlink >= 256 kbps COMM QPSK, LDPC r=1/2
SYS-05 COMM-02: >= 4 usable GS passes/day COMM Tashkent, 10 deg min el.
SYS-06 ADCS-02: Reaction wheels >= 1 mNm torque ADCS 3x CubeWheel
SYS-10 ADCS-03: Magnetorquer dipole >= 0.2 Am^2 ADCS Air-core rods
SYS-12 EPS-01: Solar generation >= 5 W (orbit avg, EOL) EPS GaAs + deployable
SYS-12 EPS-02: Battery capacity >= 25 Wh usable (EOL) EPS 4S1P NCR18650B
SYS-13 OBC-01: Safe mode entry < 10 seconds OBC Autonomous watchdog

3. Concept of Operations (CONOPS)

3.1 Mission Timeline

Day     Phase              Key Activities
-----   ---------          --------------------------------
  0     LAUNCH             Separation from deployer
  0     LEOP               Antenna deployment (30 min timer)
                           Kill switch release
                           First beacon TX
 0-1    DETUMBLE           B-dot detumbling (magnetorquers)
                           First GS pass, telemetry reception
 1-3    COMMISSIONING-1    Subsystem checkout (EPS, OBC, COMM)
                           GNSS first fix
                           Solar panel deployment
 3-7    COMMISSIONING-2    ADCS calibration (mag + sun sensors)
                           Camera first light
                           S-band link verification
 7-14   EARLY OPS          First science images
                           Radiation sensor activation
                           IoT payload commissioning
 14+    NOMINAL OPS        Routine science operations
                           Weekly imaging campaigns
                           Continuous radiation monitoring
 12 mo  MID-LIFE REVIEW    Performance assessment
                           Orbit maintenance decision
 24 mo  END OF LIFE        Passivation (battery discharge)
                           Transponder off
                           Natural deorbit begins

3.2 Nominal Operations Concept

Per-Orbit Activity Timeline (95.7 min orbit):

Time(min) Activity              Power Mode       Notes
--------  ---------             ----------       -----
  0:00    Eclipse entry         ECLIPSE_STANDBY  Heater active if needed
  0:00    Radiation monitoring  NOMINAL          Continuous background
 15:00    GNSS fix attempt      NOMINAL          Update orbit state
 33:30    Eclipse exit          NOMINAL          Solar charging resumes
 40:00    ADCS pointing (if scheduled) SCIENCE   Point at target
 42:00    Image capture         SCIENCE          3 sec exposure
 43:00    ADCS return to nadir  NOMINAL          Default orientation
 50:00    GS pass (if visible)  COMM             UHF TM + S-band data
 58:00    GS pass ends          NOMINAL          Resume standby
 62:00    Housekeeping TM store NOMINAL          Log to SD card
 95:42    Orbit complete        --               Next orbit begins

3.3 Ground Segment Operations

Activity Frequency Duration Personnel
Automated beacon monitoring Continuous - 0 (automated)
Scheduled TM downlink pass 4-6 per day 8-12 min each 1 operator
Command uplink session 1-2 per day 5 min 1 operator + 1 reviewer
Science planning Weekly 2 hours 1 scientist + 1 operator
Orbit determination update Daily 30 min Automated (GNSS)
Anomaly response As needed Variable 2+ personnel

4. Orbit Selection Rationale

Parameter Value Rationale
Type Sun-Synchronous (SSO) Consistent lighting for imaging, thermal stability
Altitude 550 km Balance: 30m GSD achievable, 7-22 year deorbit
Inclination 97.59 deg SSO requirement for 550 km
LTAN 10:30 Morning crossing: low cloud cover, good illumination angle
Expected Lifetime 2 years (nominal), 5+ years (possible) Atmospheric drag at 550 km
Orbital Period 95.7 min ~15 orbits/day

4.1 Altitude Trade Study

Altitude GSD Deorbit (yr) Eclipse (min) Link Margin Selected
400 km 23 m 2-5 36 +16 dB UHF No (short life)
500 km 29 m 5-12 35 +14 dB UHF No (marginal GSD)
550 km 32 m 7-22 34 +14 dB UHF Yes
600 km 35 m 12-30 33 +13 dB UHF No (exceeds 25yr)
700 km 40 m 50+ 31 +12 dB UHF No (debris risk)

5. Risk Register

5.1 Technical Risks

ID Risk Likelihood Impact Risk Level Mitigation
R-01 ADCS fails to detumble Low High Medium B-dot algorithm tested in HITL; magnetorquers oversized 10x
R-02 Battery degradation exceeds model Medium High High Conservative DoD (15%), redundant cell monitoring, heater
R-03 S-band link margin insufficient Low Medium Low Upgraded to 2.4m dish GS antenna; LDPC coding; fallback to UHF only
R-04 Camera optics misalignment (vibration) Medium Medium Medium Epoxy-bonded lens; vibration test at qualification level
R-05 Solar panel deployment failure Low Critical Medium Redundant burn wires; spring-loaded hinges; ground test >10 cycles
R-06 Software crash / watchdog loop Medium Medium Medium Watchdog timer; safe mode fallback; flight-proven RTOS patterns
R-07 Radiation-induced SEU (single event upset) Medium Low Low EDAC on memory; TMR on critical registers; periodic scrubbing
R-08 Thermal violation (battery overheat) Medium High High Thermal isolators; heater control; duty-cycle limits in software
R-09 Antenna fails to deploy Low Critical Medium Redundant deployment mechanism; 30-min timer + ground command backup
R-10 GNSS fails to acquire fix in orbit Low Low Low Orbit propagator fallback (SGP4); TLE upload from ground

5.2 Programmatic Risks

ID Risk Likelihood Impact Mitigation
R-11 Launch delay > 6 months High Medium Flexible launch broker; multiple manifests
R-12 Key personnel unavailable Medium Medium Cross-training; documentation
R-13 Budget overrun on GS equipment Low Low Phased procurement; borrow equipment
R-14 Frequency coordination delayed Medium High Apply to IARU early; have backup frequencies
R-15 Component obsolescence Low Medium Maintain approved vendor list; buy spares early

5.3 Risk Matrix

            Impact -->
            Negligible  Minor  Moderate  Major  Critical
  Very       |         |      |         |       |
  High       |         |      |         |       |
             +---------+------+---------+-------+---------
  High       |         | R-11 |         |       |
             +---------+------+---------+-------+---------
  Medium     |    R-07 | R-06 | R-04    | R-02  |
             |         | R-12 |  R-08   |       |
             +---------+------+---------+-------+---------
Likelihood   |    R-10 | R-13 | R-03    | R-01  | R-05
  Low        |         |      | R-14    |       | R-09
             +---------+------+---------+-------+---------
  Very       |         |      | R-15    |       |
  Low        |         |      |         |       |
             +---------+------+---------+-------+---------

Legend: Green = acceptable, Yellow = monitor, Red = mitigate actively

6. Launch Vehicle Interface

6.1 Deployer Compatibility

Deployer Vendor Envelope Mass Limit Interface Compatible
P-POD Mk III Cal Poly 3U (100x100x340.5mm) 4.0 kg Rail + spring Yes
ISIPOD ISIS 3U (100x100x340.5mm) 4.0 kg Rail + spring Yes
QuadPack ISIS 4x 3U 4.0 kg each Rail + spring Yes
NRCSD NanoRacks 6U (can accommodate 3U) 4.0 kg (3U) Rail Yes

6.2 CDS Compliance Checklist

Requirement CDS Section Status
Maximum mass 4.0 kg 3.2.1 Compliant (2.84 kg with margin)
Dimensions 100x100x340.5 mm 3.2.2 To be verified (fit check)
Rail material: AL 7075 or equiv. 3.2.4 Compliant (AL 6061-T6, approved)
Rail surface finish Ra < 1.6 um 3.2.5 To be verified (profilometer)
CG within 2 cm of geometric center 3.2.9 Compliant (9mm offset)
No hazardous materials 3.3.1 Compliant (Li-ion qualified)
Deployment switches (2x) 3.4.1 Compliant (Endurosat KS-01)
Remove-Before-Flight pin 3.4.2 Compliant (RBF disables TX)
No RF emission before deployment 3.4.3 Compliant (30-min timer)
Battery charge state 30-50% at launch 3.5.1 Procedure in place

6.3 Launch Environment (Generic LEO Rideshare)

Parameter Value Source
Quasi-static acceleration 6.5 g (axial), 2.0 g (lateral) Launcher user manual
Random vibration 14.1 g_rms (qualification) GEVS-SE
Acoustic 140 dB OASPL Launcher user manual
Shock (separation) 1000 g SRS at 1 kHz Deployer spec
Thermal (pre-launch, fairing) +10C to +40C Launcher user manual
Depressurization rate < 5 kPa/s Launcher user manual

7. Ground Segment Architecture

+--------------------+     Internet     +------------------+
|  Mission Control   |<================>| Data Processing  |
|  Center (MCC)      |                  | Server           |
|  - Pass planning   |                  | - TM archival    |
|  - Command gen.    |                  | - Image processing|
|  - Health monitor  |                  | - Science data   |
+--------+-----------+                  +------------------+
         |
         | LAN / VPN
         |
+--------v-----------+
|  Ground Station     |
|  Tashkent           |
|  - UHF Yagi + rotor |
|  - S-band dish       |
|  - SDR (USRP B210)  |
|  - GS software       |
|  - Auto-tracking     |
+--------+------------+
         |
         | RF (437 MHz / 2.4 GHz)
         |
    ~~~~~v~~~~~
    Satellite
    ~~~~~~~~~~~

7.1 Ground Station Equipment List

Item Model/Spec Purpose
UHF Antenna 9-element cross Yagi, RHCP TT&C link
S-band Antenna 2.4m parabolic dish, RHCP Science data downlink
Rotator Yaesu G-5500 (Az/El) Antenna tracking
SDR Ettus USRP B210 (70MHz-6GHz) Modem (TX/RX)
LNA (UHF) NooElec SAWbird+ (NF=0.5dB) Signal amplification
LNA (S-band) Custom (NF=0.7dB, G=25dB) Signal amplification
PA (UHF uplink) 4W, 430-440 MHz Command uplink
Computer Linux workstation GS software host
UPS 1 kVA Power backup
GPS Receiver u-blox M8 Time synchronization (UTC)

8. Mission Phases Detailed

8.1 LEOP (Launch and Early Orbit Phase) – Days 0-1

Event Time After Deploy Automated Action
Separation from deployer T+0 Yes Kill switches release
Deployment timer starts T+0 Yes 30-min wait (CDS req.)
Battery check T+1 min Yes Verify SOC > 20%
OBC boot sequence T+1 min Yes Load flight config
Antenna deployment T+30 min Yes Burn-wire activation
First beacon TX T+31 min Yes UHF beacon at 0.1 Hz
ADCS sensors ON T+32 min Yes Magnetometer + gyro
B-dot detumble start T+33 min Yes Magnetorquer control
First GS contact T+1-8 hr GS TM reception, initial assessment
Detumble complete T+3-5 hr Yes Angular rate < 0.5 deg/s

8.2 Commissioning – Days 1-14

Day Activity Success Criterion
1-2 EPS checkout: solar current, battery V/I/T All values in expected range
2-3 COMM checkout: UHF link quality, S-band test > 95% packet success, S-band sync
3-4 GNSS first fix, orbit determination Position fix < 10m, velocity < 0.1 m/s
4-5 Solar panel deployment (if deployable) Panel current increase confirmed
5-6 ADCS calibration: mag bias, sun sensor alignment Residuals < 1% FS
6-7 ADCS pointing test: nadir lock Pointing error < 5 deg
7-8 Camera first light (test image) Image received and decoded
8-10 ADCS fine pointing (reaction wheels) Pointing error < 1 deg
10-12 Payload commissioning (radiation, IoT) Data received and validated
12-14 End-to-end mission rehearsal Full imaging + downlink cycle

9. Data Budget

9.1 Daily Data Generation

Source Rate Daily Volume Priority
OBC Housekeeping 48 bytes/s 4.1 MB High
EPS Telemetry 72 bytes/s 6.2 MB High
ADCS Attitude 84 bytes/s 7.3 MB Medium
GNSS Position 5 bytes/s 0.4 MB Low
COMM Status 3 bytes/s 0.3 MB Low
Radiation Data 0.3 bytes/s 0.03 MB Medium
Camera (2 images/day) Burst 6 MB High
Total daily generation   ~24 MB  
Link Passes/day Per-pass Volume Daily Total
UHF 6 240 KB 1.4 MB
S-band 4 6.9 MB 27.6 MB
Total downlink     29.0 MB

Margin: 29.0 / 24.0 = 1.21 (21% data margin) – adequate for nominal operations. Onboard storage (32 GB SD) provides ~1,300 days of buffering at full rate.

10. References

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