Van Allen ProbesSpacecraft Operations

July 29, 2015

Kristin Fretz

JHU/APL

240-228-5386

kristin.fretz@jhuapl.edu

2

Van Allen Probes Summary Both observatories continue to operate

nominally Spacecraft, ground system, and

instruments are continually monitored and anomalies are tracked

Trending reviews held every 6 months with subsystems and instruments reporting on:

GS

/SC

F

GS

/US

N

MO

C S

/W

INS

T

SC

GS

/SC

F

GS

/US

N

MO

C S

/W

INS

T

SC

GS

/SC

F

GS

/US

N

MO

C S

/W

INS

T

SC

GS

/SC

F

GS

/US

N

MO

C S

/W

INS

T

SC

2012 2013 2014 2015

0

1

2

3

4

5

Age of Open ARs by Distribution and Status Type

Open

Monitor

Dispositioned

Diagnosed

Nu

mb

er o

f A

Rs

Last review held on June 9, 2015; no new concerns indicated by a review of current trending data

Engineering team continues to support project science in evaluating changes to orbits and spacecraft operations

Subsystem or instrument performance Overview of major subsystem/instrument

activities Anomalous behaviors (address any open

ARs) Changes in nominal operating conditions Trends that could impact future operations

3

Ground & Operations Highlights

Average Daily Data Return Average daily return for the

past year SCA: 13.9Gbits SCB: 13.9Gbits

Consistently exceeding 5.9Gb data per day requirement from each spacecraft

Regular Activities Decouple operations allows independent operation of the spacecraft and

instruments Non-critical real time contacts unattended; ground system executes Contact Plan Critical event contacts are staffed (e.g., precession maneuvers every 3 weeks) Monitor spacecraft, instruments, and ground system for anomalies Ground HW replacement plan in place; moved to new RAID system in Dec. 2014 Currently no full GSW updated scheduled

4

Spacecraft Highlights (1 of 3)

G&C/Propulsion All trended parameters

are behaving within limits

Both spacecraft require a spin down maneuver; targeting August 20

Monitor propellant usage and provide estimates of predicted end of life

Spacecraft Predicted Life SCA SCB

Remaining useable propellant – June 2015 (kg) 39.4 ± 0.82 39.5 ± 0.81

Holdout for disposal (kg)* 16.10 16.49

Available for extended mission (kg) 23.27 23.05

Avg. prop usage per maneuver (kg)** 0.308 0.287

Nominal SC life expected in orbit (years)*** 3.98 4.23

Uncertainty in predicted life estimate (+/-years) 0.25 0.26

     

Estimated nominal EOM May-19 June-19

Current Estimate (June 2015)

* Based on 20.9 yr, 2-burn disposal maneuver; passivation waiver required** Average propellant usage per maneuver between 2015 and 2019*** Assumes 19 E-W precession maneuvers/year

Mission Design/Navigation Routinely perform 1-week and 2-week comparisons of prediction

accuracy All trajectory requirements are currently being satisfied Monitor for potential conjunctions (0 high interest events in the last 6

months) Designing science related orbit changes as needed

5

Spacecraft Highlights (2 of 3)

Telecommunications All data (except SSPA supply

current) are within expected limits

SSPA trend shows excessive decrease in DC current draw

Assuming trend continues, the mission meets requirements (2.8-dB margin at end of 8 yrs)

Thermal All trended parameters behaving within expected limits Temperatures not expected to increase since material properties not

expected to degrade IEM/FSW

All trended parameters behaving within expected limits Monitor and track SBC corrected error counts, SSR total error counts,

single event upsets, etc.

6

Spacecraft Highlights (3 of 3)

PDU/PGS All trended parameters

behaving within expected limits Completed extended mission

analysis of power systems operations through Nov. 2020

Adequate power system margins through the extended mission

Solar Array has sufficient capabilities to complete the extended mission (solar array degradation less than predicted)

Battery cycle and calendar life are predicted to meet the extended mission

Autonomy/FM All key parameters are within expected limits Continually monitor LVS, Software LVS, and LBSOC thresholds

Adjusted in accordance with eclipse seasons Work with PGS Subsystem to determine when degradation of battery or SA

will require fine adjustments of thresholds

7

On-Going Work

As understood by the engineering team, the #1 science goal is to maximize mission lifetime

GOAL: Operate through early 2019

Any changes to the orbit are evaluated by engineering team Propellant is the limiting item for mission life EOL power analysis shows sufficient power through Nov. 2020 Radiation analysis on worst case part predicts total dose of 20krad in Feb. 2022

Evaluated various orbit changes for science team: Lapping Events

Continue to evaluated on a case-by-case basis

Typically use 40-70g propellant

N-S Maneuver Science team decided to eliminate N-S maneuvers after December 2014

Decreases mission life by 1-2 months/maneuver

Lower Sun Offset Angle / Widen E-W Component Science team decided remain at 19°north sun offset angle component

Lowering N-S component would result in shadowing of EFW booms

Apogee Maneuver Science team decided to adjust apogees of both spacecraft by 70km

Decreases mission life by 1-2 months

8

Deorbit Maneuver

Looking at adjusting de-orbit strategy to conserve propellant for a longer life and possibly adjust orbit of one spacecraft

Requirements Must deorbit within 25 years

Passivate battery and propulsion system

Multiple maneuver strategy Next to last burn would meet 25 year requirement

Last burn would use ‘Propellant Uncertainty’ to shorten orbit lifetime

Working with Scott Hull (GSFC) to revise plan Would require a waiver to NASA-STD-8719.14A Process for Limiting

Orbital Debris

9

Summary

Both observatories continue to operate nominally

No new concerns indicated by a review of current trending data

Engineering team continues to support project science in evaluating changes to orbits and spacecraft operations for extended mission

Radiation effects analyzed; less severe than predicted EOL power analysis completed; sufficient power exists Rework end of mission plan; possible changes to deorbit strategy

to extend propellant life

Questions?