Document:

<PAGE>   1
                                                                   EXHIBIT 4.2.1

                             SKYSTREAM CORPORATION
                               FIRST AMENDMENT TO
                  SECOND AMENDED AND RESTATED RIGHTS AGREEMENT
                             DATED FEBRUARY 5, 1999

        This Amendment is made as of the 22nd day of March, 1999, by and among
SkyStream Corporation, a California corporation (the "Company") and the
undersigned purchasers listed on the signature page hereto under the heading
Purchasers (collectively, the "Purchasers").

        WHEREAS, the Company desires to raise additional capital through the
sale of additional shares of Series C Preferred Stock;

        WHEREAS, the Company and certain of the Purchasers are parties to the
Second Amended and Restated Rights Agreement dated February 5, 1999 (the
"Agreement") to which the Purchasers of the additional shares of Series C
Preferred Stock shall be granted registration rights and rights of participation
with respect to the Preferred Shares;

        IT IS HEREBY AGREED THAT certain sections of the Agreement as set forth
below, are hereby amended:

1.      The fifth and sixth paragraphs under the section heading "Recitals" that
        currently read as follows:

        "WHEREAS, the parties understand the Purchasers on Exhibit B represent
the participants in the first closing under the Purchase Agreement and that
additional participants may invest in one or more second closings to be held no
later than 60 days thereafter; provided, however, that the aggregate number of
shares of Series C Preferred sold to the Purchasers shall not exceed 2,000,000
shares. The Existing Shareholders agree that such additional Purchasers shall be
treated as Purchasers hereunder upon such party's execution of a supplemental
signature page to this Agreement and the addition of such person's name to
Exhibit B hereto. Thereafter, the participants in closings after the first
closing, but not later than 60 days thereafter, shall be Purchasers for purposes
of this Agreement.

        NOW, THEREFORE, in consideration of the mutual promises and covenants
hereinafter set forth, the parties agree as follows:"

are amended to read in their entirety as follows:

        "NOW, THEREFORE, in consideration of the mutual promises and covenants
hereinafter set forth, the parties agree as follows:

        The parties understand the Purchasers on Exhibit B represent the
participants in the first closing under the Purchase Agreement and that
additional participants may invest in one or more second closings to be held on
March 22, 1999 and on or prior to 60 days from March 22, 1999; provided,
however, that the aggregate number of shares of Series C Preferred sold to the
Purchasers shall not exceed 3,415,000 shares. The Existing Shareholders and the
Purchasers agree that such additional Purchasers shall be treated as Purchasers
hereunder upon such party's execution of a supplemental signature page to this
Agreement and the addition of such person's name to Exhibit B hereto.
Thereafter, the participants in closings after the first closing, but not later
than 60 days from March 22, 1999, shall be Purchasers for purposes of this
Agreement."

<PAGE>   2

2.      Except as amended as set forth above, the Agreement shall continue in
        full force and effect.

        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

The Company:                   SKYSTREAM CORPORATION
                                      a California corporation

                                      By:   /s/ James D. Olson
                                            --------------------------------
                                               James D. Olson, President

The Purchasers:                       BROADCAST TRUST

                                      By:    /s/ George A. Pavlov
                                            --------------------------------
                                      Name:     George A. Pavlov
                                              ------------------------------
                                      Title:   Administrative Trustee
                                               -----------------------------

                               WENDELL G. & ETHEL S. VAN AUKEN, AUKEN
                               TTEEs, THE WENDELL G & ETHEL S. VAN
                               TRUST U/D/T 09/17/75

                                      By: /s/ W. G. Van Auken
                                          ----------------------------------

                                      MAYFIELD VIII,
                                      A CALIFORNIA LIMITED PARTNERSHIP
                               By:    MAYFIELD VIII MANAGEMENT, L.L.C.
                                      A DELAWARE LIMITED LIABILITY
                                      COMPANY, its General Partner

                                      By: /s/ George A. Pavlov
                                          --------------------------------------
                                          George A. Pavlov, Authorized Signatory

        [First Amendment to Second Amended and Restated Rights Agreement]

<PAGE>   3

The Purchasers: (continued)          MAYFIELD ASSOCIATES FUND III,
                                     A CALIFORNIA LIMITED PARTNERSHIP
                              By:    MAYFIELD VIII MANAGEMENT, L.L.C.
                                     A DELAWARE LIMITED LIABILITY
                                     COMPANY, its General Partner

                                     By: /s/ George A. Pavlov
                                         --------------------------------------
                                         George A. Pavlov, Authorized Signatory

                                     INSTITUTIONAL VENTURE PARTNERS VII
                                     By Its General Partner
                                     Institutional Venture Management VII

                                     By: /s/ Geoffrey Y. Yang
                                         ----------------------------------
                                                  Geoffrey Y. Yang
                                                  General Partner

                                     INSTITUTIONAL VENTURE
                                     MANAGEMENT VII

                                     By:  /s/ Geoffrey Y. Yang
                                         ----------------------------------
                                                   Geoffrey Y. Yang
                                                   General Partner

                                     IVP FOUNDERS FUND I, L.P.
                                     By Its General Partner
                                     Institutional Venture Management
                                     VI, L.P.

                                     By:  /s/ Geoffrey Y. Yang
                                         ----------------------------------
                                                   Geoffrey Y. Yang
                                                   General Partner

        [First Amendment to Second Amended and Restated Rights Agreement]

<PAGE>   4

The Purchasers: (continued)               IVP BROADBAND FUND I, L.P.
                                          By Its General Partner
                                          IVP Broadband Management, LLC
                                          By Its Managing Director
                                          Institutional Venture Management
                                          VIII, LLC

                                          By:  /s/ GEOFFREY Y. YANG
                                              ----------------------------------
                                                        Geoffrey Y. Yang
                                                        Managing Director

                                          NORWEST VENTURE PARTNERS VII, LP
                                          By:    Itasca VC Partners VII, LLP
                                                 Its General Partner

                                          By:  /s/ PROMOD HAQUE
                                              ----------------------------------
                                                        Promod Haque
                                                        General Partner

                                          WS INVESTMENTS

                                          By:  /s/ ROBERT P. LATTA
                                              ----------------------------------

                                          LATTA FAMILY TRUST

                                          By: /s/ ROBERT P. LATTA
                                              ----------------------------------
                                                   Robert P. Latta, Trustee

                                              /s/ T.S. HOLLIFIELD
                                              ----------------------------------
                                                   Ted S. Hollifield

                                              /s/ MARIANNE S. BRADLEY
                                              ----------------------------------
                                                   Marianne S. Bradley

       [First Amendment to Second Amended and Restated Rights Agreement]<PAGE>   1
                                                                   EXHIBIT 4.2.2

                              SKYSTREAM CORPORATION
                               SECOND AMENDMENT TO
                  SECOND AMENDED AND RESTATED RIGHTS AGREEMENT
                DATED FEBRUARY 5, 1999, AS AMENDED MARCH 22, 1999

        This Amendment is made as of the 9th day of June, 1999, by and among
SkyStream Corporation, a California corporation (the "Company") and the
undersigned purchasers listed on the signature page hereto under the heading
Purchasers (collectively, the "Purchasers").

        WHEREAS, the Company desires to raise additional capital through the
sale of additional shares of Series C Preferred Stock;

        WHEREAS, the Company and certain of the Purchasers are parties to the
Second Amended and Restated Rights Agreement dated February 5, 1999, as amended
(the "Agreement") to which the Purchasers of the additional shares of Series C
Preferred Stock shall be granted registration rights and rights of participation
with respect to the Preferred Shares;

        IT IS HEREBY AGREED THAT certain sections of the Agreement as set forth
below, are hereby amended:

1.      The fifth and sixth paragraphs under the section heading "Recitals" that
        currently read as follows:

        "WHEREAS, the parties understand the Purchasers on Exhibit B represent
the participants in the first closing under the Purchase Agreement and that
additional participants may invest in one or more second closings to be held no
later than 60 days thereafter; provided, however, that the aggregate number of
shares of Series C Preferred sold to the Purchasers shall not exceed 2,000,000
shares. The Existing Shareholders agree that such additional Purchasers shall be
treated as Purchasers hereunder upon such party's execution of a supplemental
signature page to this Agreement and the addition of such person's name to
Exhibit B hereto. Thereafter, the participants in closings after the first
closing, but not later than 60 days thereafter, shall be Purchasers for purposes
of this Agreement.

        NOW, THEREFORE, in consideration of the mutual promises and covenants
hereinafter set forth, the parties agree as follows:"

are amended to read in their entirety as follows:

        "NOW, THEREFORE, in consideration of the mutual promises and covenants
hereinafter set forth, the parties agree as follows:

        The parties understand the Purchasers on Exhibit B represent the
participants in the first and second closings under the Purchase Agreement and
that additional participants may invest in a closing to be held on June 9, 1999;
provided, however, that the aggregate number of shares of Series C Preferred
sold to the Purchasers shall not exceed 3,804,000 shares. The Existing
Shareholders and the Purchasers agree that such additional Purchasers shall be
treated as Purchasers hereunder upon such party's execution of a supplemental
signature page to this Agreement and the addition of such person's name to
Exhibit B hereto. Thereafter, the participants in closings after the first and
second closings, but not later than June 9, 1999, shall be Purchasers for
purposes of this Agreement."

<PAGE>   2

2.      Section 1.14 of the Agreement shall be amended to read in its entirety
        as follows:

        "1.14 Transfer of Registration Rights. The rights to cause the Company
to register Registrable Securities granted under this Section 1 may be assigned
by a Holder to a transferee or assignee who acquires (i) at least 300,000 of the
Registrable Securities held by such Holder or, if less, (ii) all of the
Registrable Securities then held by such Holder, provided in either case, the
Company is, within a reasonable time prior to such transfer, furnished with
written notice of the name and address of such proposed transferee or assignee
and the securities with respect to which such registration rights are being
assigned; provided further that such assignment shall be effective only if the
transferee enters into a written agreement providing that such transferee shall
be bound by the provisions of Section 1 of this Agreement. Notwithstanding the
foregoing or any other provision contained herein to the contrary, the right to
cause the Company to register Registerable Securities may be assigned by a
Holder to any constituent partner of a partnership Holder and any subsidiary or
parent of a corporate Holder provided that such transferee agrees in writing to
be bound by the terms and conditions of this Agreement."

3.      Section 2.1(a) of the Agreement shall be amended to read in its entirety
        as follows:

        "(a) Right of Participation. Subject to the terms and conditions
contained in this Section 2.1, the Company hereby grants to each Purchaser who
is the Holder of not less than 300,000 shares of Registrable Securities, the
right of participation to purchase its Pro Rata Portion of any New Securities
(as defined in subsection 2.1(b)) which the Company may, from time to time,
propose to sell and issue. A Holder's "Pro Rata Portion" for purposes of this
Section 2.1 is the ratio that (x) the sum of the number of shares of the
Company's Common Stock then held by such Purchaser and the number of shares of
the Company's Common Stock issuable upon conversion of the Preferred Stock then
held by such Holder, bears to (y) the sum of the total number of shares of the
Company's Common Stock then outstanding and the number of shares of the
Company's Common Stock issuable upon conversion of the then outstanding
Preferred Stock."

4.      Except as amended as set forth above, the Agreement shall continue in
        full force and effect.

                (Remainder of this page intentionally left blank)

<PAGE>   3

        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

The Company:                              SKYSTREAM CORPORATION
                                          a California corporation

                                          By: /s/ JAMES D. OLSON
                                              ----------------------------------
                                                  James D. Olson, President

The Purchasers:                           BROADCAST TRUST

                                          By: /s/ GEORGE A. PAVLOV
                                              ----------------------------------

                                          Name:  George A. PaVlov
                                                --------------------------------

                                          Title:  Authorized Signatory
                                                --------------------------------

                                          WENDELL G. & ETHEL S. VAN AUKEN,
                                          TTEEs, THE WENDELL G & ETHEL S. VAN
                                          AUKEN TRUST U/D/T 09/17/75

                                          By:  /s/ W. G. VAN AUKEN
                                              ----------------------------------

                                          MAYFIELD VIII,
                                          A CALIFORNIA LIMITED PARTNERSHIP
                                   By:    MAYFIELD VIII MANAGEMENT, L.L.C.
                                          A DELAWARE LIMITED LIABILITY
                                          COMPANY, its General Partner

                                          By: /s/ W. G. VAN AUKEN
                                              ----------------------------------
                                              Wendell Van Auken, Managing Member

       [Second Amendment to Second Amended and Restated Rights Agreement]

<PAGE>   4

The Purchasers: (continued)               MAYFIELD ASSOCIATES FUND III,
                                          A CALIFORNIA LIMITED PARTNERSHIP
                                   By:    MAYFIELD VIII MANAGEMENT, L.L.C.
                                          A DELAWARE LIMITED LIABILITY
                                          COMPANY, its General Partner

                                          By:  /s/ W. G. VAN AUKEN
                                              ----------------------------------
                                              Wendell Van Auken, Managing Member

                                          INSTITUTIONAL VENTURE PARTNERS VII
                                          By Its General Partner
                                          Institutional Venture Management VII

                                          By: /s/ GEOFFREY Y. YANG
                                              ----------------------------------
                                                        Geoffrey Y. Yang
                                                        General Partner

                                          INSTITUTIONAL VENTURE
                                          MANAGEMENT VII

                                          By: /s/ GEOFFREY Y. YANG
                                              ----------------------------------
                                                        Geoffrey Y. Yang
                                                        General Partner

                                          IVP FOUNDERS FUND I, L.P.
                                          By Its General Partner
                                          Institutional Venture Management
                                          VI, L.P.

                                          By: /s/ GEOFFREY Y. YANG
                                              ----------------------------------
                                                        Geoffrey Y. Yang
                                                        General Partner

       [Second Amendment to Second Amended and Restated Rights Agreement]

<PAGE>   5

The Purchasers: (continued)               IVP BROADBAND FUND I, L.P.
                                          By Its General Partner
                                          IVP Broadband Management, LLC
                                          By Its Managing Director
                                          Institutional Venture Management
                                          VIII, LLC

                                          By: /s/ GEOFFREY Y. YANG
                                              ----------------------------------
                                                        Geoffrey Y. Yang
                                                        Managing Director

                                          NORWEST VENTURE PARTNERS VII, LP
                                          By:    Itasca VC Partners VII, LLP
                                                 Its General Partner

                                          By: /s/ PROMOD HAQUE
                                              ----------------------------------
                                                        Promod Haque
                                                        General Partner

                                          WS INVESTMENTS

                                          By: /s/ ROBERT P. LATTA
                                              ----------------------------------

                                          LATTA FAMILY TRUST

                                          By: /s/ ROBERT P. LATTA
                                              ----------------------------------
                                                    Robert P. Latta, Trustee

                                          /s/ T. S. HOLLIFIELD
                                          ----------------------------------
                                          Ted S. Hollifield

                                          ----------------------------------
                                          Marianne S. Bradley

       [Second Amendment to Second Amended and Restated Rights Agreement]

<PAGE>   6

                                          INTEL CORPORATION

                                          By:  /s/ Satish Rishi
                                              ----------------------------------
                                                   Satish Rishi

                                          Title:   Assistant Treasurer
                                                 -------------------------------

       [Second Amendment to Second Amended and Restated Rights Agreement]

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