Preliminary Design of the e XTP Satellite Institute

Preliminary Design of the e. XTP Satellite Institute of Spacecraft System Engineering , CAST Hong Bin Mar 22 th , 2017 , Beijing

Outlines 1. General Description 2. Design Evolution 3. Basic Parameters 4. Preliminary Design 5. Programme Schedule 6. Problems 7. Conclusions

1. General Description • e. XTP , the enhanced X-ray Timing and Polarimetry mission, is a science mission designed to study the state of matter under extreme conditions of density , gravity , and magnetism. • It’s the next generation of the X-ray detected telescope after HXMT in China. HXMT e. XTP

2. Design Evolution 2007 The conception of XTP was put forward by IHEP; 2008 -2012 An advanced research of the XTP was carried out by ISSE; 2013 -2014 Completed the system analysis and achieved the mission’s basic parameters. The first step design of the XTP was finished; 2015 -2016 With the LAD and WFM adding into the XTP and the parameters of SFA&PFA has changed，redesigned the e. XTP satellite; 2017 New launch vehicle; new orbit；new payload；So we update the design of the e. XTP satellite.

3. Basic Parameters Orbit Launch vehicle Launch site Mass 550 km, 0 deg LM-7 Wenchang Satellite Launch Center ≤ 4500 kg 3300 W 35 m 2 Ka-band 3. 2 Tb per day 1500× 2 Mbps Launch Mass Max demand Power Solar array Frequency Band Communication Data Volume Data Rate Accuracy of attitude < 0. 01° (3σ) pointing Control system Accuracy of attitude < 0. 002° (3σ) measurement Attitude Stabilization Mission duration 0. 005°/s(3σ), 1’/500 s (3σ) 8 years（goal 15 years）

4. Preliminary Design Ø Launch Vehicle • LM-7 launch vehicle ，has a big fairing with diameter of 4200 mm a total height of 10300 mm， has maximum capacity for 550 km circular orbit at 0 deg. inclination is 4500 kg. Ø Telemetry and Control system • The TC system applies the international USB system. Low tilt angle communication is achieved through utilizing relay satellites or building new TC station. Ø Satellite ground application system • Data receiving is achieved by stations at Sanya. Or using the ground station at Malindi (3°S Kenya), built by Italian (LOFT team).

4. Preliminary Design Ø Observation Mode——Pointing Observation • The –X axis point to the specific objects in the inertial space ； • The sun vector is controlled in XOZ plane and in a obtuse angle with the +Z axis； • The sun vector will perpendicular to the solar array by rotate it； • According to the user’s observation plan to carry out attitude maneuver， aiming at the burst objects to carry on the observation. Objects

4. Preliminary Design Ø Flight Procedure Objects Burst source

4. Preliminary Design Ø Configuration Stowed in fairing On orbit

4. Preliminary Design Ø Configuration

4. Preliminary Design Ø Configuration • Service module(SVM): the SVM includes all units required to control and operate the S/C platform. The WFM and GRM are accommodated in the SVM, too. • LAD Assembly(LADA): the LADA consists of LAD panel(#1~#4), LAD sunshields, deployment mechanisms. The LADA are accomodated on either sides of the SVM. • Mirror Assembly Module(MAM): the MAM is located inside the telescope tube , contains the SFA & PFA mirror module and star trackers， with the associated supporting platform. • Telescope Tube(TT): the TT allows to maintain the SFA&PFA at the required distance from the focal planes. • Focal Plane Assembly (FPA) : the FPA hosts the 13 focal plane cameras, including thermal control hardware.

4. Preliminary Design Ø Service module(SVM) : • Hosts all platform subsystems; -four tanks -six reaction wheels -two star trackers -four sun acquisition senors -three gyroscopes • Support the LAD，WFM and GRM; • Downside of SVM is the interface of the launch vehicle; • Inside the SVM there’s a contamination cover , it’s also the sun-shield of the WFM.

4. Preliminary Design Ø Mirror Assembly(MA) : • SFA and PFA are accomodated in the mirror platform. • Conceived as independent unit. • Can be later integrated into the telescope support structure. • Kinematic mounts : Minimising the impact of mechanical and thermal -elastic loads onto the optics alignment.

4. Preliminary Design Ø LAD Assembly • Two wings (each wings two panels or one panel（TBD）); • LAD support platform use the hign thermal conductivity material for the structure; • The deployment mechanisms perform the connection between LAD panel and satellite, withstand the launch loads in the stowed condition; • On orbit, the DM releases the panel reliably, and then performs the deployment of the LAD payloads, with the automatic latching at the end of its travel; • After the latching, the DM maintains the angular position and assure the stiffness. 10 modules each panel 1973(L)× 1212(B)× 132(H) 20 modules each panel（TBD） 2384(L)× 1973(B)× 132(H)

4. Preliminary Design Ø Telescope Tube(TT) : • Maintain the required focal length; • Support the solar array and ka-antenna; • Provide the catching interface for on-orbit servicing(TBD); • The ICU of the focal detectors are accomodated on top of the TT;

4. Preliminary Design Ø Focal Plane Assembly(FPA) : • Hosts the 13 focal plane cameras; • With the sun-shield to protect the detectors from the suns; • The shape is designed to minimize the envelope dimesions and fit the fairing;

4. Preliminary Design Ø TCS: Mirror assembly thermal design • The insulating washers(fiberglass) are used to limit the conductive heat transfer between the MA and MSP. • The MA are covered by 15 -layer MIL to insulate heat radiation of SVM. • The external surface of TT is used for radiator of the MA. PFA: 20± 2℃ SFA: 20± 2℃

4. Preliminary Design Ø TCS: SDD thermal design • The FPA is connected to the TT by insulating washers, to limit the conductive heat transfer between the SDD and FPSP. • The SDD are covered by 10 -layer MIL. • The SDD heat dissipation are firstly collected by the ethane loop heat pipe, then the collected heat dissipation is refrigerated by the pulse-tube refrigerator(5 W@180 K , power 120 W). Finally, the hot junction heat dissipation of refrigerator is transmitted to the individual radiator by the ethane heat pipe. Pulse-tube Cryocooler Ethane loop heat pipe SFA-SDD *11： -110℃~-80 ℃ Radiator

4. Preliminary Design Ø TCS- LAD thermal design • Extensile sun-shield is used for the LAD, to insulate heat radiation from the sun. • The inside of the sunshield, covered by 15 -layer MIL to insulate heat radiation. • The LAD heat dissipation(5. 4 W*40=216 W) is radiated by itself. • Electric heaters(50 W power) are applied in LAD for maintaining the -20℃ lower limit. extensile sunshield LAD: -20~-10℃

5. Programme Schedule • Phase A: 2017. 01~2017. 12, international coordination, feasibility design ~2017. 08, Subsystem interface definition document (IDS) ~2017. 10, Subsystem requirements document ~2017. 12, System feasibility design • Phase B: 2018. 01~2018. 12, Preliminary design ~2018. 09, Subsystem preliminary design ~2018. 12, System preliminary design • Phase C: 2019. 01~2021. 12, System critical design ~2019. 01 SM delivery(30% for special test(TBD)) ~2019. 12 EM delivery ~2020. 12 SM and TM delivery ~2021. 06 QM completed • Phase D: 2022. 01～ 2024. 06, Flight model and launch ~2022. 06 FM delivery • Phase E: 2025. 01～ 2035. 10, Science observation

5. Programme Schedule Ø Payload equipment requirements STM Deliverable EM Deliverable QM Non-deliverable FM Deliverable FS Deliverable as required SFA mirror assembly (SFM) 9 - 2 9 2 PFA mirror assembly (PFM) 4 - 1 4 1 SFA camera assembly (SFC) 9 9 2 PFA camera assembly (PFC) 4 4 1 DHU-F 4 4 1 4 - PCDU 1 1 1 2 - LAD module 40 40 40 10 LAD PBEE 4 4 1 4 - 2+2 1+1 2+2 - WFM Camera 6 6 1 6 2 WFM ICU 2 2 1 2 - LAD ICU: DHU(2)+PDU(2) 21

6. Problems Ø LAD Assembly The following key requirements should be confirmed: • Panels: ~The interface between panel structure and sun-shield, DM, module, PBEE. ~The requirements for strength, stiffness, alignment, thermo-stability, material, connection style. ~The technical flow about the delivery, assembly, test(How? Where? ). • LAD sun-shield: ~The requirements for materials, frequency, weight, thermal control. ~Interface of the HDRM. • Deployment Mechanisms: ~The interface between DM and the panels. ~Requirements for Frequency, Accuracy, Drive torque, Thermo-stability, Weight. ~AIT process and items.

6. Problems Ø WFM The requirements for installation accuracy, consistency of direction (for one pair) Can you accept the state that Fo. V is blocked or change the point angle(decide by the LAD panels and sunshield)？ The URF could meet the launch loads and on-orbit thermal environment？ If CAST responsibility for the design of WFM support structure: Can you adjust the position of the three URF？(Insufficient Operation Space) Can you redesign the position of the electrical connector？(Insufficient Operation Space for 3 pairs)

7. Conclusions • We have updated the design of e. XTP satellites, which could meet the requirement of the science; • Something should be confirmed to help us understanding the design and requirements of the science.

Thanks for your attention！ 探索宇宙奥秘 造福人类社会