Automation of Operations for a Spacecraft in Geo Transfer Orbit

Automation of Operations for a Spacecraft in Geo Transfer Orbit | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Automation of Operations for a Spacecraft in Geo Transfer Orbit Praful H Roy, Akram M Y, Shreedhar P Kulkarni, Subramani R, Srinivasa Murthy D, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8280178/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Operating a spacecraft in an elliptical geo transfer orbit throughout the mission life presents multiple constraints and unique operational challenges. The long-term operation at lower perigee altitudes in the presence of atmospheric drag compounds momentum build-up and necessitates optimized momentum desaturation cycles. When perigee height is not maintained, atmospheric drag affects the apogee height. Reaction wheel speeds vary drastically with each perigee passage and due to external disturbances, requiring periodic thruster operations to maintain wheel speeds within limits and ensure stable attitude. To address these complexities, operational strategies have evolved from initial manual ground commands to automation with effective utilization of onboard features, notably leveraging the On-Board Timer (OBT) system for all key tasks such as solar array positioning at perigee, eclipse operations, auto momentum dumping during non-visibility periods, perigee raising maneuvers and payload operations. Attitude control switches efficiently between inertial (sun-safe) and payload (earth-oriented) modes to achieve operational requirements amidst time-varying visibility windows and frequent eclipses. Comprehensive automation was progressively implemented to manage constraints like overhead pass, varying signal and power levels, and limited station visibility without using external station support, ultimately allowing the spacecraft to maintain service and optimize payload usage in an elliptical orbit. This progression streamlined ground resource usage and provided valuable lessons for future satellite missions operating under non-ideal conditions and prolonged orbit raising, such as electric propulsion system-based orbit raising. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Spacecraft not designed or intended to operate in highly elliptical geo transfer orbits (GTO), is to be maintained and controlled either due to any unforeseen mission requirement or because of anomalies, face challenges not found in synchronous missions. Persistent low perigee orbit, variable atmospheric drag, fuel and power constraints, and shifting visibility windows for ground control station make operation complex. However, adopting step-by-step evolution from manual ground-driven commands, auto scheduling of events to onboard autonomy features, such spacecraft can operate successfully for service, payloads, and data continuity. The paper presents the automation approaches, operational results, and lessons learned from the long-term management of such a spacecraft. The detailed case draws on a recent mission where a navigation satellite, stranded in GTO following an onboard anomaly that limited the orbit raising functionality, operated successfully through evolving ground procedures and onboard autonomy features. The discussion is intentionally anonymized for generic relevance, and references masked data and approaches fit for any future missions facing similar challenges. 2. Operational Challenges in Geo Transfer Orbits Spacecraft in GTO experience alternating visibility and non-visibility zones over their target region. Visibility is defined relative to ground station access over, for example, the Indian region. These cycles lead to periodic AOS (Acquisition of Signal) and LOS (Loss of Signal) intervals, demanding discrete operational profiles. The visibility duration follows a 6-day profile as shown in the Fig. 2.1 . Operating a spacecraft in a prolonged elliptical orbit (220 × 38,000km) poses many intertwined technical and operational challenges. 2.1 Atmospheric Drag and Orbit Decay Low perigee altitudes subject the spacecraft to significant atmospheric drag during each orbit. Drag not only reduces apogee, shortening orbital lifetime, but imparts disturbance torques that complicate attitude control. The exposed area, atmospheric density (varying with space weather), and residual velocity exacerbate the problem in highly elliptical orbits. 2.2 Momentum Management Disturbance forces near perigee, such as atmospheric drag, cause momentum to rise resulting in actuators to diverge from nominal operating ranges, often above acceptable limits. Momentum dumping is scheduled to occur primarily near apogee and during favourable orientations to help in increasing perigee and preserving satellite control. The process is managed through automated command execution utilizing on-board timer feature with pulse width adjustments using remote programming feature. 2.3 Attitude and Power Management The spacecraft is operated in inertial sun-safe and earth-pointed mode for payload operation. Inertial sun-safe mode is used during non-visibility to meet thermal constraint of atomic clocks and manage thermal, power budgets. Earth-pointed mode is initiated during Indian region visibility for -aiding user services, such as navigation and communication. Optimizing solar array orientation during perigee cross over is crucial: panels are oriented to minimize drag, and at other times track the sun to maximize power input. 2.4 Ground Operations and Communication GTO spacecraft move rapidly relative to Earth’s surface, resulting in short and shifting ground station visibility window. Limited elevation window due to Overhead passes (e.g., Full Coverage Antenna (FCA): Elevation between 10° & 80°, Full Motion Antenna (FMA): Elevation between 10° & 84°), station blockages puts additional constraint on continuous commanding capability and telemetry reception. This forces high reliability requirements on scheduled operations used onboard features. 2.5 Data Link Constraints and Payload Operations As the orbit is not synchronous, visibility and available service time over the region varies daily. Payloads operate primarily during regional visibility. Operations begin following AOS and end before LOS with scheduling for attitude steering profiles, state vector updates, required mode changes for beam pointing (e.g., 83°E, 5°N), sun search for panel normalization, payload activation, then reorientation and payload shutdown. Highly elliptical orbits cause large changes in ground-spacecraft range, changing signal power. High Doppler shifts (up to 40 kHz) and long-range variations challenge both satellite and ground receivers, limiting the intervals for effective payload operation. 3. Automation Strategy for Attitude and Orbit Control Transitioning from ground-dependent to autonomous operations was pivotal to mission continuity. 3.1 Daily Generation and Uploading of OBT Files Manual control—panel slews, attitude mode changes, momentum dumping—proved unsustainable due to command opportunity limitations and risk of missing critical periods (perigee, eclipse entry/exit, ground station overhead pass blocks). The solution was using and enhancing available onboard automation features, including the On-Board Timer (OBT), Event Based Commanding (EBC), and Auto Charge Cut-off (ACO) to schedule and execute all mission events. Operational teams generate daily OBT files encompassing all routine events for spacecraft control, sequencing time-tagged operations such as: Perigee pre- and post-solar array positioning Momentum dumping enable and disable State vector coefficient initiation ASP (Attitude Steering Profile) initiation at AOS, payload ON, BOA (Back of Attenuation) setting, ASP termination before LOS Sun search and open loop profile rate selection during ASP Sun-safe mode transition 3.2 On-Board Timer (OBT) System OBT acts as a programmable scheduler allowing timed execution of solar array slews at every perigee (± 30 min), orienting arrays 90° away from the velocity vector to minimize drag, then returning to sun-pointing elsewhere. OBT triggers attitude state transitions at AOS and LOS, minimizing risk during non-visibility and optimizing ground link events. Angular momentum thresholds are checked every five minutes, and if exceeded, and outside threshold windows, thrusters fire sequentially (yaw/roll/pitch) for short pulses (typically five seconds). 3.3 Control Modes and Logic Two operational modes alternate based on visibility: Inertial (Sun-Safe) Mode, selected using Safe Qs during non-visibility (or when visibility is less than four hours), prioritizing atomic clock safety, power, and thermal management (payloads disabled). ASP (Payload) Mode, enabled during regional visibility, with beam pointing, CDMA ranging, and payload operations sequenced for service benefit. 3.4 Battery Management Eclipse and charging operations require careful management. On board feature EBC is programmed to initiate battery charge based on programmed voltage limit and ACO terminates charge. 3.5 Automation Algorithms and Flexibility Momentum thresholds, panel slew angles, and payload windows are parametric and reconfigurable by ground command, allowing on-orbit adjustments to environmental changes (e.g., drag increase, prolonged eclipse). Sequence of Events (SOE) generation is crucial part of this automation. Scheduling all critical operations such as momentum dumping, orbit co-efficient uplink, subsequent day SOE uplink in terms of OBT commands, orbit co-efficient Init, payload ON sequence and payload OFF sequence require efficient mission management strategy and precise automation tool. This automation software interfaces various inputs available at flight dynamics server such as orbital elements, orbital events like AOS, LOS, Perigee, Apogee, eclipse entry & exit, static database like ground station antenna minimum elevation angle, spacecraft mission database for command formation. After satisfying operational conditions and constraints a complete SOE is generated. The generated SOE is verified, validated and auto copied to operational computers in the form of uplink ready command file format. These command files are finally integrated into daily schedule and gets executed automatically based on timeline. The automation software was developed in Java and uses SQL for database management and event scheduling. It was Tested and evaluated thoroughly in test environment and operationalized. Flowchart of this software shown in Fig. 3.5 .1 clearly brings out all the modules involved in this software. 4. Detailed Methods for Momentum Desaturation and Perigee Raising Maneuvers Attitude control constantly samples body momentum, comparing it to set limits (e.g., 1.5 Nms). When the threshold is reached (except perigee ± 45 min, payload operation), a command is queued for the appropriate axis. Thruster pulsing uses remotely patched pulse widths (set at five seconds considering minimal thrust). The need for dumping in yaw, roll, or pitch is checked every five minutes, ensuring balanced momentum distribution. Each perigee pass results in a net loss of orbital energy; burning at apogee maximizes perigee raise. Operational teams executed a series of planned, low-thrust burns (~ 4×30 sec per day) over several weeks. With only MMH (monomethyl hydrazine)-based attitude thrusters, the perigee height was gradually raised despite limited capability. Burn commands are preloaded in OBT, time-tagged for apogee positions, ensuring maneuvers occur even during station non-visible period. Thermal environment of propulsion elements was controlled to maximize output realized from thrusters. Figure 4.1 shows perigee increased from 170 km to 280 km, improving orbital lifetime and payload opportunities. 5. Results and Performance Automating visibility and non-visibility zone operations and shifting routines (panel slews, momentum handling, payload windows, attitude transitions) into OBT files produced meaningful gains: Routine ground commands reduced to bare minimum. Wheel speeds remained within safe limits; loss-of-control events were minimized. Payload services continued, with optimized operational windows. Cell balancing and battery management preserved power margins, even with repeated eclipse exposures. A typical daily sequence includes: AOS + 1 hr: SV (State Vector) Init SV Init + 5 min: Earth pointing Selection Earth pointing Selection + 20 min: Array Sun Search Array Sun Search + 5 min: Profile Mode Select Profile Mode Select + 5 min: CDMA RX ON RX ON + 10 min: Payload ON Before LOS: Payload OFF, revert to inertial orientation control, enable auto momentum dumping 6. Lessons Learnt from Long-Term Operation in Elliptical Orbits Moving to full OBT-based control made the mission robust. Explicit scheduling around perigee and eclipse periods reduced disturbance-induced failures. Dynamic tuning and frequent reviews of automation logic enabled real-time responses to orbital changes, ultimately preserving mission health. Careful sequencing of operations reduced risks. 7. Conclusion The case dealt in this paper demonstrates that spacecraft left in highly elliptical geo transfer orbits can deliver valuable service if operational philosophies are quickly transitioned from manual, event-driven to adaptive, automated regimens. With the right blend of on-board autonomy (OBT, EBC, etc.,) careful resource management, and robust ground procedures, even missions initially deemed “crippled” can achieve much of their intended potential and are a source of crucial lessons for future orbit anomaly recoveries. Declarations Competing interests: Not applicable Author Contribution PHR and AMY wrote manuscript text and SPK,SR,SMD and KK reviewed the manuscript, GSC provided coding support Data Availability Internal data was used in the research work Additional Declarations No competing interests reported. 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08:57:20","extension":"xml","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":26820,"visible":true,"origin":"","legend":"","description":"","filename":"01412064da634842a210ffcbefcc970d1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/3ce48b04e8c477caacf22543.xml"},{"id":100564920,"identity":"0eaf6b7e-c0ad-4bf5-949b-c4fd77ceb983","added_by":"auto","created_at":"2026-01-19 08:57:20","extension":"html","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":33075,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/ba6c612fdb2a8ba54d66d40c.html"},{"id":100564884,"identity":"75f75255-380e-4b7b-8ae8-efd92ea10206","added_by":"auto","created_at":"2026-01-19 08:57:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":57155,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 2.1:\u003c/strong\u003eVariation in visibility duration follows a six-day cycle. This plot illustrates how the daily ground station visibility window varies due to the spacecraft's elliptical orbit, highlighting the scheduling and operational planning required.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/7c8ed81c1e6b8ef0f4088449.png"},{"id":100594917,"identity":"a1a7e7c7-4d20-4920-8872-66acdae7b4a3","added_by":"auto","created_at":"2026-01-19 13:46:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":65169,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 3.5.1:\u003c/strong\u003eFlowchart of Automated SOE Generation Process. This diagram summarises the automation workflow for SOE generation, validation, command file preparation, schedule integration, and automatic execution in on-orbit operations.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/f7f9a0dabef797ee60a2d6de.png"},{"id":100564886,"identity":"f7640f7a-f645-49dc-8186-be0e68162c08","added_by":"auto","created_at":"2026-01-19 08:57:20","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":314818,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 3.5.2 \u003c/strong\u003eOBT 1553 Dump. This screenshot shows the 1553 bus data dump of the On-Board Timer (OBT), including queued automated command sequences, operational time tags, and critical event scheduling.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/4e09c4681c5619960a624e7e.png"},{"id":100564888,"identity":"e6c10782-6100-433a-9bab-1899cf23ccd1","added_by":"auto","created_at":"2026-01-19 08:57:20","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":283776,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 3.5.3 \u003c/strong\u003eHardware OBT Dump. This snapshot shows the OBT command executions.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/d927a12558ec0bf1b37f023a.png"},{"id":100595638,"identity":"c0b3ce26-8573-4058-9ce0-12e536938e77","added_by":"auto","created_at":"2026-01-19 13:48:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":353739,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 3.5.3 \u003c/strong\u003eTypical Sequence of Events. The flow diagram presents the logical order of operations automatically executed within a daily OBT file\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/65ea46a301e7f80fdcd77441.png"},{"id":100595174,"identity":"0d9544c4-6212-4b5d-87ff-280b612611a2","added_by":"auto","created_at":"2026-01-19 13:47:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":112585,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.4.1\u003c/strong\u003ePerigee Altitude Variation with and without Maneuver. Comparative plot showing perigee altitude evolution over time—one trajectory without periodic perigee-raising maneuvers and one with OBT-scheduled apogee burns. The effect of routine maneuvers on orbital maintenance and mission lifetime extension is clear.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/1b2f65193593c62fc068565b.png"},{"id":100796082,"identity":"57584d9c-0dea-45bd-8300-7094425324c4","added_by":"auto","created_at":"2026-01-21 13:39:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2027976,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8280178/v1/d90ec4da-bb3f-4bde-99e2-fce602e6ed9e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Automation of Operations for a Spacecraft in Geo Transfer Orbit","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSpacecraft not designed or intended to operate in highly elliptical geo transfer orbits (GTO), is to be maintained and controlled either due to any unforeseen mission requirement or because of anomalies, face challenges not found in synchronous missions. Persistent low perigee orbit, variable atmospheric drag, fuel and power constraints, and shifting visibility windows for ground control station make operation complex. However, adopting step-by-step evolution from manual ground-driven commands, auto scheduling of events to onboard autonomy features, such spacecraft can operate successfully for service, payloads, and data continuity. The paper presents the automation approaches, operational results, and lessons learned from the long-term management of such a spacecraft. The detailed case draws on a recent mission where a navigation satellite, stranded in GTO following an onboard anomaly that limited the orbit raising functionality, operated successfully through evolving ground procedures and onboard autonomy features. The discussion is intentionally anonymized for generic relevance, and references masked data and approaches fit for any future missions facing similar challenges.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Operational Challenges in Geo Transfer Orbits","content":"\u003cp\u003eSpacecraft in GTO experience alternating visibility and non-visibility zones over their target region. Visibility is defined relative to ground station access over, for example, the Indian region. These cycles lead to periodic AOS (Acquisition of Signal) and LOS (Loss of Signal) intervals, demanding discrete operational profiles. The visibility duration follows a 6-day profile as shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2.1\u003c/span\u003e. Operating a spacecraft in a prolonged elliptical orbit (220 \u0026times; 38,000km) poses many intertwined technical and operational challenges.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Atmospheric Drag and Orbit Decay\u003c/h2\u003e \u003cp\u003eLow perigee altitudes subject the spacecraft to significant atmospheric drag during each orbit. Drag not only reduces apogee, shortening orbital lifetime, but imparts disturbance torques that complicate attitude control. The exposed area, atmospheric density (varying with space weather), and residual velocity exacerbate the problem in highly elliptical orbits.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Momentum Management\u003c/h2\u003e \u003cp\u003eDisturbance forces near perigee, such as atmospheric drag, cause momentum to rise resulting in actuators to diverge from nominal operating ranges, often above acceptable limits. Momentum dumping is scheduled to occur primarily near apogee and during favourable orientations to help in increasing perigee and preserving satellite control. The process is managed through automated command execution utilizing on-board timer feature with pulse width adjustments using remote programming feature.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Attitude and Power Management\u003c/h2\u003e \u003cp\u003eThe spacecraft is operated in inertial sun-safe and earth-pointed mode for payload operation. Inertial sun-safe mode is used during non-visibility to meet thermal constraint of atomic clocks and manage thermal, power budgets. Earth-pointed mode is initiated during Indian region visibility for -aiding user services, such as navigation and communication. Optimizing solar array orientation during perigee cross over is crucial: panels are oriented to minimize drag, and at other times track the sun to maximize power input.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Ground Operations and Communication\u003c/h2\u003e \u003cp\u003eGTO spacecraft move rapidly relative to Earth\u0026rsquo;s surface, resulting in short and shifting ground station visibility window. Limited elevation window due to Overhead passes (e.g., Full Coverage Antenna (FCA): Elevation between 10\u0026deg; \u0026amp; 80\u0026deg;, Full Motion Antenna (FMA): Elevation between 10\u0026deg; \u0026amp; 84\u0026deg;), station blockages puts additional constraint on continuous commanding capability and telemetry reception. This forces high reliability requirements on scheduled operations used onboard features.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Data Link Constraints and Payload Operations\u003c/h2\u003e \u003cp\u003eAs the orbit is not synchronous, visibility and available service time over the region varies daily. Payloads operate primarily during regional visibility. Operations begin following AOS and end before LOS with scheduling for attitude steering profiles, state vector updates, required mode changes for beam pointing (e.g., 83\u0026deg;E, 5\u0026deg;N), sun search for panel normalization, payload activation, then reorientation and payload shutdown. Highly elliptical orbits cause large changes in ground-spacecraft range, changing signal power. High Doppler shifts (up to 40 kHz) and long-range variations challenge both satellite and ground receivers, limiting the intervals for effective payload operation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Automation Strategy for Attitude and Orbit Control","content":"\u003cp\u003eTransitioning from ground-dependent to autonomous operations was pivotal to mission continuity.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Daily Generation and Uploading of OBT Files\u003c/h2\u003e \u003cp\u003eManual control\u0026mdash;panel slews, attitude mode changes, momentum dumping\u0026mdash;proved unsustainable due to command opportunity limitations and risk of missing critical periods (perigee, eclipse entry/exit, ground station overhead pass blocks). The solution was using and enhancing available onboard automation features, including the On-Board Timer (OBT), Event Based Commanding (EBC), and Auto Charge Cut-off (ACO) to schedule and execute all mission events. Operational teams generate daily OBT files encompassing all routine events for spacecraft control, sequencing time-tagged operations such as:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ePerigee pre- and post-solar array positioning\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMomentum dumping enable and disable\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eState vector coefficient initiation\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eASP (Attitude Steering Profile) initiation at AOS, payload ON, BOA (Back of Attenuation) setting, ASP termination before LOS\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSun search and open loop profile rate selection during ASP\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSun-safe mode transition\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 On-Board Timer (OBT) System\u003c/h2\u003e \u003cp\u003eOBT acts as a programmable scheduler allowing timed execution of solar array slews at every perigee (\u0026plusmn;\u0026thinsp;30 min), orienting arrays 90\u0026deg; away from the velocity vector to minimize drag, then returning to sun-pointing elsewhere. OBT triggers attitude state transitions at AOS and LOS, minimizing risk during non-visibility and optimizing ground link events. Angular momentum thresholds are checked every five minutes, and if exceeded, and outside threshold windows, thrusters fire sequentially (yaw/roll/pitch) for short pulses (typically five seconds).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Control Modes and Logic\u003c/h2\u003e \u003cp\u003eTwo operational modes alternate based on visibility:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eInertial (Sun-Safe) Mode, selected using Safe Qs during non-visibility (or when visibility is less than four hours), prioritizing atomic clock safety, power, and thermal management (payloads disabled).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eASP (Payload) Mode, enabled during regional visibility, with beam pointing, CDMA ranging, and payload operations sequenced for service benefit.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Battery Management\u003c/h2\u003e \u003cp\u003eEclipse and charging operations require careful management. On board feature EBC is programmed to initiate battery charge based on programmed voltage limit and ACO terminates charge.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Automation Algorithms and Flexibility\u003c/h2\u003e \u003cp\u003eMomentum thresholds, panel slew angles, and payload windows are parametric and reconfigurable by ground command, allowing on-orbit adjustments to environmental changes (e.g., drag increase, prolonged eclipse).\u003c/p\u003e \u003cp\u003eSequence of Events (SOE) generation is crucial part of this automation. Scheduling all critical operations such as momentum dumping, orbit co-efficient uplink, subsequent day SOE uplink in terms of OBT commands, orbit co-efficient Init, payload ON sequence and payload OFF sequence require efficient mission management strategy and precise automation tool.\u003c/p\u003e \u003cp\u003eThis automation software interfaces various inputs available at flight dynamics server such as orbital elements, orbital events like AOS, LOS, Perigee, Apogee, eclipse entry \u0026amp; exit, static database like ground station antenna minimum elevation angle, spacecraft mission database for command formation. After satisfying operational conditions and constraints a complete SOE is generated. The generated SOE is verified, validated and auto copied to operational computers in the form of uplink ready command file format. These command files are finally integrated into daily schedule and gets executed automatically based on timeline.\u003c/p\u003e \u003cp\u003eThe automation software was developed in Java and uses SQL for database management and event scheduling. It was Tested and evaluated thoroughly in test environment and operationalized.\u003c/p\u003e \u003cp\u003eFlowchart of this software shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3.5\u003c/span\u003e.1 clearly brings out all the modules involved in this software.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Detailed Methods for Momentum Desaturation and Perigee Raising Maneuvers","content":"\u003cp\u003eAttitude control constantly samples body momentum, comparing it to set limits (e.g., 1.5 Nms). When the threshold is reached (except perigee\u0026thinsp;\u0026plusmn;\u0026thinsp;45 min, payload operation), a command is queued for the appropriate axis. Thruster pulsing uses remotely patched pulse widths (set at five seconds considering minimal thrust). The need for dumping in yaw, roll, or pitch is checked every five minutes, ensuring balanced momentum distribution.\u003c/p\u003e \u003cp\u003eEach perigee pass results in a net loss of orbital energy; burning at apogee maximizes perigee raise. Operational teams executed a series of planned, low-thrust burns (~\u0026thinsp;4\u0026times;30 sec per day) over several weeks. With only MMH (monomethyl hydrazine)-based attitude thrusters, the perigee height was gradually raised despite limited capability. Burn commands are preloaded in OBT, time-tagged for apogee positions, ensuring maneuvers occur even during station non-visible period. Thermal environment of propulsion elements was controlled to maximize output realized from thrusters. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4.1\u003c/span\u003e shows perigee increased from 170 km to 280 km, improving orbital lifetime and payload opportunities.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"5. Results and Performance","content":"\u003cp\u003eAutomating visibility and non-visibility zone operations and shifting routines (panel slews, momentum handling, payload windows, attitude transitions) into OBT files produced meaningful gains:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eRoutine ground commands reduced to bare minimum.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eWheel speeds remained within safe limits; loss-of-control events were minimized.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePayload services continued, with optimized operational windows.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eCell balancing and battery management preserved power margins, even with repeated eclipse exposures.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eA typical daily sequence includes:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eAOS\u0026thinsp;+\u0026thinsp;1 hr: SV (State Vector) Init\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSV Init\u0026thinsp;+\u0026thinsp;5 min: Earth pointing Selection\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEarth pointing Selection\u0026thinsp;+\u0026thinsp;20 min: Array Sun Search\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eArray Sun Search\u0026thinsp;+\u0026thinsp;5 min: Profile Mode Select\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eProfile Mode Select\u0026thinsp;+\u0026thinsp;5 min: CDMA RX ON\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eRX ON\u0026thinsp;+\u0026thinsp;10 min: Payload ON\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eBefore LOS: Payload OFF, revert to inertial orientation control, enable auto momentum dumping\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"6. Lessons Learnt from Long-Term Operation in Elliptical Orbits","content":"\u003cp\u003eMoving to full OBT-based control made the mission robust. Explicit scheduling around perigee and eclipse periods reduced disturbance-induced failures. Dynamic tuning and frequent reviews of automation logic enabled real-time responses to orbital changes, ultimately preserving mission health. Careful sequencing of operations reduced risks.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"7. Conclusion","content":"\u003cp\u003eThe case dealt in this paper demonstrates that spacecraft left in highly elliptical geo transfer orbits can deliver valuable service if operational philosophies are quickly transitioned from manual, event-driven to adaptive, automated regimens. With the right blend of on-board autonomy (OBT, EBC, etc.,) careful resource management, and robust ground procedures, even missions initially deemed \u0026ldquo;crippled\u0026rdquo; can achieve much of their intended potential and are a source of crucial lessons for future orbit anomaly recoveries.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests:\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003ePHR and AMY wrote manuscript text and SPK,SR,SMD and KK reviewed the manuscript, GSC provided coding support\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eInternal data was used in the research work\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8280178/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8280178/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOperating a spacecraft in an elliptical geo transfer orbit throughout the mission life presents multiple constraints and unique operational challenges. The long-term operation at lower perigee altitudes in the presence of atmospheric drag compounds momentum build-up and necessitates optimized momentum desaturation cycles. When perigee height is not maintained, atmospheric drag affects the apogee height. Reaction wheel speeds vary drastically with each perigee passage and due to external disturbances, requiring periodic thruster operations to maintain wheel speeds within limits and ensure stable attitude. To address these complexities, operational strategies have evolved from initial manual ground commands to automation with effective utilization of onboard features, notably leveraging the On-Board Timer (OBT) system for all key tasks such as solar array positioning at perigee, eclipse operations, auto momentum dumping during non-visibility periods, perigee raising maneuvers and payload operations. Attitude control switches efficiently between inertial (sun-safe) and payload (earth-oriented) modes to achieve operational requirements amidst time-varying visibility windows and frequent eclipses. Comprehensive automation was progressively implemented to manage constraints like overhead pass, varying signal and power levels, and limited station visibility without using external station support, ultimately allowing the spacecraft to maintain service and optimize payload usage in an elliptical orbit. This progression streamlined ground resource usage and provided valuable lessons for future satellite missions operating under non-ideal conditions and prolonged orbit raising, such as electric propulsion system-based orbit raising.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Automation of Operations for a Spacecraft in Geo Transfer Orbit","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-19 08:57:15","doi":"10.21203/rs.3.rs-8280178/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8a7e8732-aee7-4cf8-98af-d8213324d1f6","owner":[],"postedDate":"January 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-28T18:23:29+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-19 08:57:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8280178","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8280178","identity":"rs-8280178","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}