SOHO Commisioning Phase

In this page:

Overview of Commissioning Operations
Service Module and Payload Commissioning Blocks
Joint Operations

J3 Script

Commissioning Operations Timeline
DSN Schedule for SOHO Contacts
Weekly Operations Schedule
Daily Operations Schedule
Daily Meetings & Reports
Instrument Anomaly Reports (Access from the EOF/EAF only)

Overview of Commissioning Operations

The Transfer Trajectory Phase will start once the Centaur upper stage of the launch vehicle has stopped its engine for the last time. This last burnout will take SOHO out of its circular parking low-earth orbit towards the Lagrange L1 point of the Sun-Earth system, some 1.5 million km sunwards from the Earth. Four months later, another maneuver will insert the spacecraft into a halo orbit around this point. Once there, the nominal science operations will soon start.

[NEW]
The SOHO transfer and halo orbits.

During this transfer phase the focus of the mission operations will be to check out all the spacecraft subsystems including the payload. The sequence and the timing of events in this phase has been carefully planned and is documented in the SOHO Commissioning Plan. A description of the planned operations, and the related timelines can be accessed from this page, and a summary is given here.

Service Module and Payload Commissioning Blocks

The operations needed to prepare the SOHO Spacecraft and each of the experiments for scientific observations have been grouped in logical units, so-called "blocks". Blocks consist of sub-blocks, which group operations which have to be carried out contiguous in time, i.e. during one DSN contact. Typically, the commissioning blocks for the experiments are:

Block 1: Switch-on, open door to crack, and start outgassing
Block 2: Functional verification (i.e. check out of mechanisms)
Block 3: Calibration of instrument (i.e. verification of scientific capability)
Block 4: Science test runs (i.e try-out of scientific programs).

However, each of the 12 experiments on-board SOHO is different, and this is reflected in deviations from this template. For example, some experiments will verify and calibrate each subsystem completely before going to the next subsystem, thus interleaving block 2 and 3. Others will not calibrate at all, and others again will perform functional verification during switch-on.

The SOHO Service Module (SVM) will verify its basic subsystems as soon as possible after launch, and will conduct further tests in relation to maneuvers and other special events in the transfer trajectory phase.

The detailed operations and scheduling constraints per block are written up in block sheets and are grouped here together with the detailed timelines per experiment, and for the SVM.

Joint Operations

In addition to the individual check-outs there are several commissioning tests that involve more than one of the experiments and/or the SVM. These tests have been discussed by the SOWG and a coordinator has been selected to assemble all the information needed and draw a plan:

Howard - J1: S/C roll maneuvre for experiment calibrations.
Charra - J2: 5 arcsecond spacecraft oscillations for GOLF.
Fröhlich - J3: 10 arcmin spacecraft offset for VIRGO.
- J3 Script (April 2, 21:00 UT)
Bush - J4: Spacecraft short term pointing stability.
Poland - J5: Spacecraft absolute pointing.
Larduinat - J6: Inter-instrument data exchange.
Bush - J7: Ground system station transfers during NRT operations.

There are also several SVM tests that require participation from the experiments. These include the ones above and the following tests described in the SVM Blocks.

Finally there is a schedule of intercalibrations between experiments, planned by the Intercalibrations Working Group (ICWG), chaired by John Kohl.

Commissioning Operations Timeline

A schedule has been made for commissioning operations from the first time the commanding link to SOHO is established (about 2 hours after launch) up to insertion into Halo Orbit, about 4 months after launch, and for sporadic activities up for two months more. Only after completing all these activities can SOHO be declared "fully operational" and start its nominal 2 years science mission, with a possible extension of 4 more years.

For the detailed planning of operations the following ground-rules have been established:

Until functional verification of Payload and SVM all operations take place during direct contact with the ground, and are carried out in sequence (no simultaneous commanding of two or more experiments). The long contacts are used for commissioning, the short contacts for regular S/C operations
Where possible 100% contingency time per ground contact is scheduled for all operations up to functional verification
In resolving scheduling conflicts SVM is given priority over Payload

A definition of the phases of the commissioning plan is given in the table below, and the timeline (when available) for each phase can be inspected by clicking on the entry. Even more detailed timelines per experiment and for the SVM can be found here.

NOTE: All the files are in PostScript format.

Launch and Early Orbit Phase (LEOP): 3 days. There are 72 hours of continuous DSN contact after launch, with 43 hours of operations after S/C contact is established and 27 hours of contingency.
Early Experiment Operations Phase (EEOP): 16 days. There are 12 hour long DSN contacts for the first 12 days, then 8 hour contacts. 75 hours of planned operations and 88 hours of contingency have been scheduled
Second Midcourse Correction (MCC2): 4 days. All passes reserved for SVM, 27 hours of operations, 24 hours of contingency.
MCC2 to Maximum Distance: 37 days. Operations not yet scheduled in full detail
Maximum Distance to Halo Orbit: 2 months. Operations not yet scheduled in full detail
Halo Orbit Commissioning: 2 months of sporadic commissioning activities, and First Month of SOHO Science

DSN Schedule for SOHO Contacts

NASA's Deep Space Network (DSN) provides for the communications between the SOHO Spacecraft and the Ground Command Facilities at NASA Goddard Space Flight Center. During normal operations SOHO will have three short contacts of 1.6 hour each, for a health check and a dump of the data recorded on the Solid State Recorder, and a daily long contact, which normally lasts for 8 hours and enables the experiment teams to carry out near-real-time (NRT) observations. This allows them to react immediately to events on the Sun, and choose observing targets with the greatest possible accuracy.

DSN provides us with three different schedules, in increasing order of accuracy:

The Strawman Schedule, last update for the week 3 weeks ahead.
The Forecasted Schedule, last update for the week, 2 weeks ahead.
The Final Schedule, last update for the upcoming week.

The daily schedules for the upcoming weeks reflect in their timing the latest DSN information, but longer term schedules obviously cannot. In the latter a start of the long contact at noon (12:00 PM) GMT has been assumed, because clock time then coincides with elapsed time since the beginning of the contact.

Weekly Operations Schedule

Daily Operations Schedule

A day by day schedule for the upcoming events is provided below:

An easy schedule for the first three days is the LEOP timeline
The day by day schedule for the Early Experiment Operations Phase, from day 4 to day 20, is given here
Graphic representation of planned operations

Daily Meetings & Reports

A daily meeting is held at the EOF to assess the status of the spacecraft and the experiments. The following documents can be inspected on-line:

Return to the Science Operations page
Last modification: December 11, 1997
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